fix(streaming): collision-ready gate -- the pawn waits for a COOKED floor, not a submitted one

WORK-NEXT item 1, plus all three of item 6. Item 2 (the fused evaluator) untouched as
instructed.

⭐ RMC DOES EXPOSE WHAT WE NEEDED, so the gate rests on a real signal:
  OnCollisionBodyUpdated                              (delegate -- diagnostic)
  SetCollisionConfig() -> TFuture<ERealtimeMeshCollisionUpdateResult>  (AUTHORITATIVE)
RealtimeMeshComponent was READ ONLY, per the owner's grant. Nothing there was modified.

THE INVARIANT
Until now nothing guaranteed a tile the player occupies has collision. apply_s ended at
mesh SUBMISSION; RMC cooks asynchronously and we recorded no completion, so no
measurement this project has ever taken said when physics could actually collide.

  - per-tile CollisionReadyTiles state, with stale-callback protection
  - HandleTileCollisionCookComplete driven by RMC's cook future
  - pawn gated at BeginPlay and pre-physics on the FEET-SUPPORT tile -- deliberately not
    the actor-centre tile, because the floor that catches a falling pawn is what must be
    cooked -- plus the predicted movement path and solid/air traversal
  - movement-component state saved/restored, so a temporary stream wait cannot
    permanently change a character's movement mode
  - new trace fields: mesh_submit_to_cook_s, collision_request_to_cook_s,
    body_event_to_future_s -- three boundaries where we had one blurred number

ITEM 6, all three:
  - LoadedTiles is now recorded only after SUCCESSFUL mesh submission, and a failed
    mesh init retries. Previously a failed init left a tile marked loaded forever -- a
    permanent hole.
  - origin spawning fixed (the zero-position guard made a pawn at exactly
    FVector::ZeroVector indistinguishable from "no pawn" -- and the owner spawns at 0,0)
  - exact core-lattice validation for uniform whole-tile verdicts, which previously had
    no safety net while block verdicts did

⚠️ I FIXED TWO COMPILE ERRORS MYSELF rather than spend another Codex round on them:
`GetMovementMode()` / `GetCustomMovementMode()` do not exist on
UCharacterMovementComponent -- MovementMode and CustomMovementMode are public fields.
Two lines. Codex did not build this round, so it could not have caught them.

VERIFIED BY ME: build 0 errors after the patch; export 1.022 / 1.055 s (aa62971 was
1.034 / 1.089); geometry SHA-256 b3e5f4c3..9b377 UNCHANGED -- generation is untouched,
as it should be for a streaming-lifecycle change.

⚠️ UNVERIFIED AND IMPORTANT: the submission-to-cook gap is still unmeasured -- Codex had
no live process to measure it in. The instrumentation exists and will report it on the
next play session. And the GATE ITSELF IS UNTESTED IN MOTION: if a support tile never
becomes collision-ready, the pawn stays frozen rather than falling. That trade is
deliberate, but the owner should watch for it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012aheo2crrZmHuYtPpdY2Cb

Source/VoxelForge/Private/VoxelStartupTrace.cpp

@@ -113,7 +113,7 @@ namespace
             if (Sample.bCacheHit) ++CacheHits;
             if (Sample.bRegionHit) ++RegionHits;
             Triangles += Sample.Triangles;
-            Request.Add(Sample.RequestToReadySeconds);
+            Request.Add(Sample.RequestToApplySeconds);
             Queue.Add(Sample.QueueWaitSeconds);
             Generation.Add(Sample.GenerationSeconds);
             Classify.Add(Sample.ClassifySeconds);
@@ -123,7 +123,7 @@ namespace
 
         return FString::Printf(
             TEXT("{\"count\":%d,\"empty\":%d,\"all_air\":%d,\"all_solid\":%d,\"mixed\":%d,\"cache_hits\":%d,\"region_hits\":%d,\"triangles\":%lld,"
-                 "\"request_ready_s\":{\"p50\":%s,\"p95\":%s,\"max\":%s},"
+                 "\"request_apply_s\":{\"p50\":%s,\"p95\":%s,\"max\":%s},"
                  "\"queue_s\":{\"p50\":%s,\"p95\":%s,\"max\":%s},"
                  "\"generation_s\":{\"p50\":%s,\"p95\":%s,\"max\":%s},"
                  "\"classify_s\":{\"p50\":%s,\"p95\":%s,\"max\":%s},"
@@ -265,11 +265,11 @@ void RecordTile(const FTileSample& Sample)
     ++GState->TileRecordsWritten;
     WriteEventLocked(*GState, TEXT("tile"), FString::Printf(
         TEXT("\"level\":%d,\"verdict\":%d,\"empty\":%d,\"cache_hit\":%d,\"region_hit\":%d,\"triangles\":%d,"
-             "\"request_to_ready_s\":%s,\"queue_wait_s\":%s,\"worker_queue_s\":%s,\"result_queue_s\":%s,"
+             "\"request_to_apply_s\":%s,\"queue_wait_s\":%s,\"worker_queue_s\":%s,\"result_queue_s\":%s,"
              "\"generation_s\":%s,\"classify_s\":%s,\"mesh_s\":%s,\"stream_s\":%s,\"apply_s\":%s"),
         Sample.Level, Sample.Verdict, Sample.bEmpty ? 1 : 0,
         Sample.bCacheHit ? 1 : 0, Sample.bRegionHit ? 1 : 0, Sample.Triangles,
-        *Number(Sample.RequestToReadySeconds), *Number(Sample.QueueWaitSeconds),
+        *Number(Sample.RequestToApplySeconds), *Number(Sample.QueueWaitSeconds),
         *Number(Sample.WorkerQueueSeconds), *Number(Sample.ResultQueueSeconds),
         *Number(Sample.GenerationSeconds), *Number(Sample.ClassifySeconds),
         *Number(Sample.MeshSeconds), *Number(Sample.StreamSeconds), *Number(Sample.ApplySeconds)));

Source/VoxelForge/Public/VoxelStartupTrace.h

@@ -15,7 +15,9 @@ namespace VoxelForgeStartupTrace
         bool bCacheHit = false;
         bool bRegionHit = false;
         int32 Triangles = 0;
-        double RequestToReadySeconds = 0.0;
+        // This is worker-result -> game-thread mesh submission. Collision readiness is a later
+        // per-tile RMC completion event recorded separately as collision_ready.
+        double RequestToApplySeconds = 0.0;
         double QueueWaitSeconds = 0.0;
         double WorkerQueueSeconds = 0.0;
         double ResultQueueSeconds = 0.0;

Source/VoxelForge/Public/VoxelTypes.h

@@ -32,8 +32,8 @@ constexpr float VOXEL_SIZE = 25.0f;
 // TRIVIAL-TILE CLASSIFICATION (T1.d)
 //=============================================================================
 // Verdict de ClassifyTile pour une tuile AVANT le pré-échantillonnage 33³+ :
-// AllSolid / AllAir garantissent que CHAQUE point du treillis du mesher (marge
+// AllSolid / AllAir guarantee every core cell vertex of the mesher (g=0..Cells;
-// ±1 incluse) est du même côté de l'iso ⇒ maillage vide, GenerateMesh est
+// the ±1 halo is normal-only) is on the same side of the iso ⇒ empty mesh, GenerateMesh is
 // sautée. Mixed = "je ne peux pas le prouver" ⇒ génération normale. Un faux
 // Mixed coûte juste du CPU ; un faux AllSolid/AllAir ferait un TROU — les
 // verdicts ne sont donc émis que sur des bornes exactes (colonnes surface

Source/VoxelForge/Public/VoxelWorld.h

@@ -16,7 +16,12 @@
 
 // Forward declaration
 class URealtimeMeshComponent;
+class URealtimeMesh;
 class URealtimeMeshSimple;
+class UBodySetup;
+class APawn;
+class UPawnMovementComponent;
+class UCharacterMovementComponent;
 class UVoxelDiffLayer;
 class UVoxelContentManager;
 class UVoxelAtmosphereManager;
@@ -81,18 +86,18 @@ struct FChunkResult
     // so the game thread only uploads them — the per-vertex builder loop was the dominant
     // game-thread cost while moving (the apply drain). TSharedPtr (not a by-value StreamSet) so
     // FChunkResult stays movable through the MPSC queue with the type only FORWARD-DECLARED here.
-    // Null ⇒ empty/all-air tile (no component).
+    // Null ⇒ no-surface tile (uniform all-air/all-solid or an empty content band; no component).
     TSharedPtr<RealtimeMesh::FRealtimeMeshStreamSet> Streams;
     uint32 Epoch = 0;         // Generation epoch — discard if stale
     // Monotonic request timestamp used only for streaming telemetry. It is carried through the
-    // worker queue so the profile can report request-to-ready, not just worker generation time.
+    // worker queue so the profile can report request-to-apply, not just worker generation time.
     uint64 RequestStartCycles = 0;
     // Worker timing boundaries for separating scheduler wait from generation and result/apply wait.
     // These are telemetry-only and remain zero when tile profiling is disabled.
     uint64 GenerationStartCycles = 0;
     uint64 GenerationEndCycles = 0; int32 ClassifyVerdict = -1; bool bClassifierCacheHit = false; bool bClassifierRegionHit = false; double ClassifySeconds = 0.0; double MeshSeconds = 0.0; double StreamSeconds = 0.0; int32 NumTriangles = 0;
     bool bAborted = false;    // Worker observed shutdown; never mark this tile loaded
-    bool bEmpty = true;       // true ⇒ all-air tile (Streams null); still marked loaded so we don't re-submit
+    bool bEmpty = true;       // true ⇒ no surface (uniform all-air/all-solid or empty band); still loaded
     // F17 — the mesher classifies every triangle semantically (sky-cap = down-facing near the
     // column's CeilSurf; overhangs/cave roofs stay ground) and packs them as two contiguous runs
     // (ground then cap) in the index buffer → polygroups 0/1 → two RMC sections with their own
@@ -193,9 +198,41 @@ public:
     // game-thread problem (this supersedes the earlier region-batching). Collision + content
     // are level-0 only.
 
-    /** Tiles fully loaded — INCLUDING empty/all-air tiles, so we never re-submit them. */
+    /** Tiles whose result was successfully applied — INCLUDING empty/all-air tiles, so we never
+     *  re-submit them. A non-empty level-0 tile is not collision-ready until its RMC cook callback
+     *  has added it to CollisionReadyTiles. */
     TSet<FVoxelTileKey> LoadedTiles;
 
+    /** Level-0 tiles whose latest submitted RMC collision body has finished cooking and was
+     *  installed. This is the authoritative collision-readiness set used by the pawn gate; mesh
+     *  submission and LoadedTiles are intentionally not sufficient. */
+    TSet<FVoxelTileKey> CollisionReadyTiles;
+
+    /** Level-0 tiles whose applied result is known to contain no surface (uniform empty/solid).
+     *  They need no BodySetup themselves, but the pawn gate may walk past them while looking for
+     *  the first resolved collidable support tile. */
+    TSet<FVoxelTileKey> CollisionNotRequiredTiles;
+
+    /** Subset of CollisionNotRequiredTiles proved all-solid. A support probe inside one of these
+     *  tiles searches upward for the boundary tile; all-air/empty tiles search downward. */
+    TSet<FVoxelTileKey> CollisionSolidTiles;
+
+    struct FPendingCollisionCook
+    {
+        TWeakObjectPtr<URealtimeMesh> Mesh;
+        uint64 SubmissionId = 0;
+        uint64 MeshSubmittedCycles = 0;
+        uint64 CollisionSubmittedCycles = 0;
+        bool bBodyUpdatedEventSeen = false;
+        uint64 BodyUpdatedEventCycles = 0;
+    };
+
+    /** One serialised completion record per tile. The serial prevents a late RMC future from
+     *  making a remeshed tile, or a pooled component reused by another tile, appear ready. */
+    TMap<FVoxelTileKey, FPendingCollisionCook> PendingCollisionCooks;
+    uint64 NextCollisionSubmissionId = 0;
+    TMap<URealtimeMesh*, FDelegateHandle> CollisionBodyUpdatedHandles;
+
     /** Render component per NON-empty loaded tile (GC-safe via actor ownership; not UPROPERTY
      *  because FVoxelTileKey isn't a USTRUCT key). */
     TMap<FVoxelTileKey, URealtimeMeshComponent*> TileComponents;
@@ -640,9 +677,11 @@ public:
 
     /**
      * Game-thread apply for one gen result (shared by ProcessPendingChunks + SyncRemeshTile):
-     * epoch check, mark loaded, ingest capture, then either release the tile's component (empty) or
+     * epoch check, ingest capture, then either release the tile's component (empty) or submit a mesh
-     * ApplyMeshToTile. Returns true iff a VISIBLE mesh was uploaded (counts against the apply budget).
+     * through ApplyMeshToTile. Returns true iff a VISIBLE mesh was submitted (counts against the
-     * Does NOT touch PendingTiles — the caller owns that.
+     * apply budget); collision readiness is a later RMC completion.
+     * Does NOT touch PendingTiles — the caller owns that. A non-empty result counts as applied only
+     * after mesh submission succeeds; collision readiness arrives asynchronously afterwards.
      */
     bool ApplyTileResult(FChunkResult& Result);
 
@@ -681,7 +720,7 @@ public:
      * the strate content band the mesh was cut to; material lookups clamp into that band).
      * Never called for empty results.
      */
-    void ApplyMeshToTile(FChunkResult& Result);
+    bool ApplyMeshToTile(FChunkResult& Result);
 
     /** Mini-sun lighting (bounded directional). Each frame writes the nearest 4 active orbs' WORLD
      *  positions (+ reach radius in .w) into OrbLightMPC's Orb0..3 vector params; the Directional
@@ -708,9 +747,39 @@ public:
     // HELPERS
     //=========================================================================
 
-    /** Get the current player position (or zero if no player) */
+    /** Return the current player position and distinguish "no pawn" from a valid origin position. */
+    bool TryGetPlayerPosition(FVector& OutPosition, APawn** OutPawn = nullptr) const;
+
+    /** Compatibility wrapper for callers that only need the location. A real pawn at the origin
+     *  therefore returns FVector::ZeroVector just like any other valid position. */
     FVector GetPlayerPosition() const;
 
+    /** Level-0 tile under the pawn's feet. This is deliberately separate from the actor-center tile:
+     *  the floor that catches a falling pawn is what must be cooked before movement is released. */
+    bool GetPlayerSupportTile(APawn* Pawn, const FVector& PlayerPosition,
+                              FVoxelTileKey& OutSupportTile) const;
+
+    bool IsTileCollisionReady(const FVoxelTileKey& Tile) const;
+    bool IsCollisionReadyFromSupportTile(const FVoxelTileKey& CandidateTile,
+                                         FVoxelTileKey* OutSupportTile = nullptr) const;
+    bool IsPlayerSupportCollisionReady(APawn* Pawn, const FVector& PlayerPosition,
+                                       FVoxelTileKey* OutSupportTile = nullptr) const;
+
+    /** Gate pawn movement until its current and, when moving, next support tile have a completed
+     *  level-0 RMC collision body. The world tick is installed as the pawn prerequisite in the
+     *  implementation (and directly on its movement component) so this check runs before
+     *  CharacterMovementComponent physics. */
+    void UpdatePawnCollisionGate(APawn* Pawn, const FVector& PlayerPosition, float DeltaTime);
+    void EngagePawnCollisionGate(APawn* Pawn);
+    void ReleasePawnCollisionGate();
+
+    /** Called by the RMC collision future after async cook + BodySetup installation. */
+    void HandleTileCollisionCookComplete(const FVoxelTileKey& Tile, uint64 SubmissionId,
+                                         URealtimeMesh* Mesh, uint8 Result);
+    void BindRealtimeMeshCollisionEvent(URealtimeMesh* Mesh);
+    void UnbindRealtimeMeshCollisionEvent(URealtimeMesh* Mesh);
+    void HandleRealtimeMeshCollisionBodyUpdated(URealtimeMesh* Mesh, UBodySetup* BodySetup);
+
     // (GetLODForChunk / LODToStep / IsChunkInRange removed — dead since the clipmap
     //  streaming replaced the distance-LOD scheme; the level lives in FVoxelTileKey.)
 
@@ -800,6 +869,23 @@ public:
     bool bStartupTraceDesiredRecorded = false;
     TArray<FVoxelTileKey> DesiredSorted;   // desired tiles, nearest-first
 
+    // PLAYER COLLISION GATE — the pawn is allowed to enter/leave a tile only when the level-0
+    // collision body covering its feet has completed the RMC cook. The movement component state is
+    // saved so a temporary stream wait does not permanently change a character's movement mode.
+    TWeakObjectPtr<APawn> PawnTickPrerequisite;
+    TWeakObjectPtr<UPawnMovementComponent> PawnMovementTickPrerequisite;
+    TWeakObjectPtr<APawn> CollisionGatedPawn;
+    TWeakObjectPtr<UPawnMovementComponent> CollisionGatedPawnMovement;
+    TWeakObjectPtr<UCharacterMovementComponent> CollisionGatedCharacterMovement;
+    uint8 SavedCharacterMovementMode = 0;
+    uint8 SavedCharacterCustomMovementMode = 0;
+    bool bSavedCharacterMovementMode = false;
+    bool bSavedPawnMovementActive = false;
+    bool bPawnCollisionGateEngaged = false;
+    bool bPawnGateWaitingForPredictedSupport = false;
+    FVoxelTileKey PawnGatePredictedSupportTile;
+    bool bPawnGateUnsupportedReported = false;
+
     // Desired-set membership STAMPÉE : clé → numéro du dernier crossing où la tuile était désirée.
     // BuildDesiredTiles upserte le stamp courant puis balaie la map UNE fois : les entrées à stamp
     // périmé sont les "leavers" (retirées + renvoyées). Le cull ne considère que ces leavers + la