perf(streaming): outer tile classifier off by default; delete mode 2

Owner-approved, on the A/B measured in 83a0e4d: the classifier plus exact validation cost more
than it saved on the game path. With it off, ready p95 is 182 vs 190-195 ms, generation p95 is
125-127 vs 139-141 ms, and density calls drop 18%.

- GVoxelForgeOuterClassifierMode defaults to 0. Mode 1 stays reachable via
  voxel.OuterClassifierMode=1 as an A/B instrument; the clamp is now 0..1.
- Mode 2 (validation samples reused as the mesher core grid) is deleted: the reuse grid,
  FVoxelMesherCoreDensityGrid, GenerateMesh's ReusableCoreGrid parameter, bValidationCoreReused,
  TotalValidationCoreReuseTiles and its log field. It could not fire: it reused the grid only
  when validation disproved a uniform verdict, which never happened, and Mixed tiles never
  validate. The mode-1 validation loop exits early again on the first disagreeing sample.
- All three GenerateMesh call sites checked; the density-count pointer binds after BandVoxHi.

Verified by Codex, checked by me against the logs:
- build ok; the measured process loaded the staged DLL, SHA-256 1024D8CF..04D
- export OBJ SHA-256 unchanged: b3e5f4c3..9b377
- a run WITHOUT the override prints outer_classifier_mode=0 validation_density_calls=0,
  proving the new default took effect
- 841/841 tiles have identical triangle counts between mode 0 and mode 1. The 394 tiles mode 1
  skipped as uniform produce 0 triangles in mode 0, so the strate band cut (applied by the
  mesher, not by validation) was not hiding geometry.

Docs: ARCHITECTURE 8.10, CODEMAP (GenerateTileResult, ClassifyTile) and fable-idea T1.d record
that streaming no longer classifies by default. WORK-NEXT item 1 records the owner's playtest:
he can no longer fall through the world.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VZS94UH8bSsBeg5sZaxe2Y

WORK-NEXT.md

@@ -28,6 +28,10 @@ The player falls through the world. There is **no invariant** that a tile you oc
 **Do**: record cook-complete; gate the pawn (spawn and movement) on the supporting tile being
 collidable, not merely applied.
 
+✅ **Owner playtest, 2026-09-13: he can no longer fall through the world.** The gate uses RMC's
+`SetCollisionConfig()` future as the authority (`HandleTileCollisionCookComplete`,
+`IsPlayerSupportCollisionReady`).
+
 📖 **Reading `Plugins/RealtimeMeshComponent` is permitted for this item — READ ONLY.** Find whether a
 cook-complete delegate/flag exists. ⛔ No edits, no builds against it: the owner's copy carries custom
 modifications and was destroyed once by an over-broad delete.
@@ -125,8 +129,14 @@ figure and does ~18% fewer density calls. It cannot remove geometry, since it sk
 *disproved* (`VoxelWorld.cpp` ~4012), and validation disproved none: 0 reuse tiles in every run. Mixed
 tiles, the ones that actually need a grid, never run validation, so there is nothing to reuse.
 
-**Recommendation, pending the owner:** set `GVoxelForgeOuterClassifierMode` default to 0. It stays
-switchable by `voxel.OuterClassifierMode`.
+**Done 2026-09-13, owner approved:** `GVoxelForgeOuterClassifierMode` now defaults to 0, and mode 2
+is deleted along with its reuse grid, its mesher parameter and its counter. Mode 1 is still
+reachable with `voxel.OuterClassifierMode=1` as an A/B instrument. Verified:
+- export OBJ SHA-256 unchanged (`b3e5f4c3..9b377`)
+- a run without the override prints `outer_classifier_mode=0 validation_density_calls=0`
+- **841/841 tiles have identical triangle counts between mode 0 and mode 1**. The 394 tiles mode 1
+  skipped as uniform produce 0 triangles in mode 0, so the strate band cut was not hiding geometry
+  behind the classifier.
 
 ⚠️ **Correction to `f204413`.** Its message says the nested classifier's 3.5x "cannot be reproduced".
 That was my measurement error: I passed `-voxel.UseBlockEarlyOut=1` (the STREAMING console variable)