feat(opstack): FRoomGraphSource::EffectOverBox answers spatially -- and AUDIT C2 is fixed

The chain no longer dies at the room source. The criterion is the per-voxel cull
lifted from point to box, which can fail for exactly one reason: Eval starts at
MinSDF = FLT_MAX and only lowers it through a primitive that survives its own
cull, so if no cached primitive survives its cull anywhere in the box, Sdf stays
FLT_MAX across the whole box.

FSdfConvertOp already returned Identity ("la source a repondu pour la paire") and
the twelve detail modifiers already inherited through VF_NoCaveOverBox. One
function learned to answer and fourteen operators became provable -- what the C1
wiring was built for.

Three deliberate choices, all erring toward CPU rather than toward a hole:
- |Perlin3D| <= 2, derived from GradDot + the convex hull of a trilinear lerp,
  instead of the header's observed "~[-1,1]". A verdict resting on an observation
  is the hole this file spends its life avoiding.
- the op pool is passed to BuildChunkCache, not nullptr: the bake reads OpParams
  to place pits and chimneys, so nullptr would under-bound the cache and could
  return Identity over a real pit.
- the search box is wider than Eval's, giving a superset of primitives.

The verdict is memoised per box (all twelve modifiers ask the same question), and
the cache is a SECOND per-worker cache so classification cannot disturb a live
generation's hot cache.

AUDIT C2, confirmed 2026-07-28, is fixed on the switch path in the same breath:
GetDensityWithParams now takes required ParamsFingerprint + LayoutVersion. The
alternative this audit section used to recommend -- add chunk Z to the key -- is
insufficient (Interleaved makes Alpha depend on chunk XY too) and destructive
(chunk XY is deliberately absent so gradient probes don't thrash the box, ARCH
8.10). The CRC is taken once per chunk where the params memo already lives, so
the per-voxel cost is two integer compares. The three test call sites pass it
too, so the oracle stops sharing the defect it tests.

Check 4 of the tunnel test no longer asserts "0 proved" -- that assertion would
now forbid the gain. It brute-forces every proved tile voxel by voxel instead and
reports the count, because a false verdict leaves no geometry and no collision
behind it.

The second debt (per-room ops can raise a modifier's amplitude above the strate
params a box bound reads) turned out to be DORMANT, not live: where the source
proves Identity the modifiers' gate never opens, and where it answers Both it
supplies no MaxCarveOverBox so nothing is provable anyway. It goes live the day
the source gains one. Written at the site.

Unbuilt.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CODEMAP.md

@@ -154,7 +154,7 @@ bit. They are port-correctness oracles, not fidelity checks: the acceptance bar
 | `FSurfaceColumnSource` (internal) | 1 | The bridge between the two spaces: consumes the ground + sky-cap **height** stacks and produces density. `IsXYPure()` **false** — the heights are XY-pure, a distance to them never is. Owns the per-column memo, keyed by `PrepareChunk` on `(StrateBottomWorldZ, LayoutVersion, Seed)` so it is **shared down the whole vertical strate stack**, exactly like `GSurfColCache`. |
 | `VoxelDensityOps::BuildSurfaceStack` | — | SurfaceWorld, complete: column + overhang + 3 structural, plus biome blending when `PerBiomeParams` is non-empty. Takes ownership of an `IVoxelBiomeField`. |
 | `VoxelDensityOps::BuildVerticalShaftStack` | — | 8 ops, and **three are Maze's reused unchanged** (`ConstantRock`, `SdfRoughness`, `SdfCarve`) with different tuning (freq 0.1 vs 0.12, window `rough+4` vs `R+rough+2`). The measured proof of `OPSTACK-PLAN §2.5`'s reuse claim. |
-| `FRoomGraphSource` (internal) | 1 | TunnelNetwork's SDF spine. **CALLS `BuildChunkCache`/`EvaluateSDFCached` — does not transcribe them**: that is where §8.4's two-region discipline lives and a copy would fork it. Owns the cave warp (scope = this op alone; pits/chimneys read *unwarped* coords, which is why no FRAME op was needed). Its cache key adds a **params CRC + LayoutVersion** that the original lacks — see the suspected staleness note in AUDIT §C2. `EffectOverBox` → `Both` for now (a real answer means building the cache for the queried box; only pays once `ClassifyTile` consumes `ClassifyBox`). |
+| `FRoomGraphSource` (internal) | 1 | TunnelNetwork's SDF spine. **CALLS `BuildChunkCache`/`EvaluateSDFCached` — does not transcribe them**: that is where §8.4's two-region discipline lives and a copy would fork it. Owns the cave warp (scope = this op alone; pits/chimneys read *unwarped* coords, which is why no FRAME op was needed). Its cache key adds a **params CRC + LayoutVersion**; the original lacked them until AUDIT §C2 was fixed (2026-07-28) and now carries them too. **`EffectOverBox` ANSWERS SPATIALLY** since 2026-07-28: it builds the cache for the queried box into a *second* per-worker cache (never `FState::Cache`), then lifts each primitive's per-voxel cull from point to box — rooms/tunnels as spheres vs the warp-dilated box, pits/chimneys vs the **undilated** box (real coords), columns as infinite cylinders. `Identity` ⇒ `Sdf` stays `FLT_MAX` ⇒ `FSdfConvertOp` **and all twelve detail modifiers** go identity with it. Verdict is memoised per box (the twelve all ask the same question). Warp dilation uses a **provable** `\|Perlin3D\| ≤ 2`, not the header's observed `~[-1,1]`. |
 | `FWormFieldSource` (internal) | 1 | Fielded 3D-noise threshold carve, masked by distance to the room network (reads `InOut.Sdf` *after* pits/chimneys). `EffectOverBox` → **`CarveOnly` everywhere** — no spatial bound, so it kills `AllSolid` on every tile of every strate with worms on. `MaxCarveAmplitude()` holds the bound from DECOMPOSITION §0.2 that would recover it, waiting for a fold that carries numbers. |
 | `VoxelDensityOps::BuildTunnelNetworkStack` | — | **COMPLETE, 19 ops** — the biggest port in the plugin (~1080 lines), done in three stages: SDF spine (A) → the twelve detail modifiers of 4b–4h (B) → the per-room op override (C). Serves **TunnelNetwork and Underwater** from one builder. Operator order is the original's, line for line, and it is load-bearing (`FFloorBiasMod` exists to undo what `FCaveRoughnessMod` did to floors). |
 | `FCaveRoughnessMod` (internal) | 3 | STEP 4b, **density space** — a different op from `MakeSdfRoughnessMod`: two octave sets, optional domain warp, four noise types, an anti-fill clamp inside definite air, quadratic fade. ⚠️ **Reads STRATE params, not the per-room copy** — the original's shadow is declared *after* step 4b. Eleven of twelve modifiers read the room copy; this one does not. |
@@ -262,7 +262,7 @@ redesign; tile identity lives in `FVoxelTileKey` (VoxelWorld.h).
 | `ApplyPassageCarving` (static) | 197 | Punches passages/elevator through the seal. |
 | `InitializeSettings` | 211 | Copies seed from settings. |
 | **`GetDensityAt`** | 218 | **Entry point.** Picks strate + generator type, dispatches, adds diff offset. |
-| **`GetDensityWithParams`** | 277 | TunnelNetwork pipeline (~1000 lines). See §4. |
+| **`GetDensityWithParams`** | 277 | TunnelNetwork pipeline (~1000 lines). See §4. ⚠️ Takes **required** `ParamsFingerprint` + `LayoutVersion` since the AUDIT §C2 fix (2026-07-28) — they go into the SDF cache key so a chunk can no longer be evaluated against a neighbour's rooms. Callers compute the CRC **once per chunk** (`CP_TunnelFP`), never per voxel. |
 | **`GetSlabDensity`** | 1306 | FlatPlain/CrystalChamber pipeline. See §4.2. |
 | `SampleSurfaceStructuralZ` | — | **F20:** the RAW SurfaceWorld heightfield (continents+mountains+detail), BEFORE any terrain op; returns terrain Z + relief M. Cliff re-samples it at an XY offset for a cheap analytic slope. |
 | `ComputeSurfaceTerrainZ` / `GetSurfaceDensity` | — | SurfaceWorld heightfield → terrain Z, then density; biome **output-blend** lerps dominant/neighbour heights (`ParamsD`/`ParamsN`/weight). **F20 surface ops** (`FSurfaceGenerationParams`, biome-selected + slope/relief-conditioned, all default off): Cliff (slope-gated STEEPENING — push height from local mean where steep ⇒ sheer walls; 4 structural resamples only when on), Terrace (relief-gated + `TerraceHardness`), LayerLines (sedimentary shelves) — pure per-column height REMAPS applied here so the single height oracle stays consistent (MC/sheets/ClassifyTile/deco/BP bridge). **Phase 2 OVERHANG** (volumetric — real jutting shelves): in `SurfaceDensityFromColumn`, for AIR voxels in a window `(TerrainZ, TerrainZ+OverhangHeight]` above a steep slope, the heightfield is re-sampled UPHILL (toward the cliff) by a reach that GROWS with height (tiny low ⇒ air over the void, full high ⇒ borrows the far cliff rock) and unioned in ⇒ a shelf attached to the cliff, tapering out over the void with air beneath (the sketch). Per-column `OverhangAmp`(=strength·slope-gate) + unit uphill `(DirX,DirY)` resolved once in `ComputeSurfaceColumn` (gradient sampled at the REACH scale so a spot over the void can see the cliff), cached on `FSurfaceColumn`. Genuine 3D (per-voxel structural re-eval, gated to steep overhang columns). Off ⇒ byte-identical. §8.14. |