perf(generation): exact worm block skip with a proven 3D Perlin bound -- measured NEUTRAL

The sampler put the worm carve's first noise call (VoxelGenerator.cpp:3985, FusedWorm) at 19.4% of
LOD0. The worm only carves where N1 + N2 < T with N2 >= 0, so where N1 >= T it contributes nothing,
bit for bit. A block proven to have N1 >= T everywhere can skip both noise calls exactly.

- The Lipschitz bound for this Perlin3D implementation: L = (15/4) * sqrt(3) * 1.25 = 8.118988160,
  in scaled-N1 units, with a 1e-3 float-rounding margin. Adversarial sampling found a worst ratio
  of 3.187 (0.39 L). The existing 2D floor-relief bound (8.5) is a component bound of a different
  field and was confirmed not to transfer.
- A soundness test that can fail (VoxelForgeWormBlockSkipTest): 6,476 proved blocks, 355,945 exact
  lattice samples, 0 violations. A deliberately halved L proves a bad block; the full L rejects it.
- voxel.WormBlockSkip, default 1.

Field exact: export OBJ byte-identical (b3e5f4c3..9b377), 841/841 keyed tiles identical to
NextHeadStaticTrace_20260913, capability 20,830 / 10,909.

RESULT, stated plainly: no measurable speed gain. The skip rate is 4.07% of worm-eligible LOD0
samples and 0% at LOD1-4, because the bound is ~2.5x looser than the worst observed ratio at the
block size used. Paired on-vs-off, two interleaved runs each: static worker +2.15%, generation p50
+1.8%; moving worker -1.42%, request p50 -2.5%. Within noise. The next round turns the default OFF.
The proven bound and its test are kept for a tighter skip later (smaller or hierarchical blocks,
or a per-cell bound).

Run ledger (from Codex's report): the first build failed on an ambiguous test overload and was
fixed; two timing runs are void because the orchestrator stopped the session so the owner could
use the PC; the eight valid timing runs, the sampler run and the diagnostics runs completed. No
new crash folders. PERF-SAMPLED.md now lists all eight earlier-round UECC crash records.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TaFdXhTdYMkW1xrV6ApT6Y

CODEMAP.md

@@ -341,7 +341,7 @@ This is **where terrain shape lives.**
 | `ApplyPassageCarving` (static) | 197 | Punches passages/elevator through the seal. |
 | `InitializeSettings` | 211 | Copies the effective seed, spine radius, and global XY world-bound settings from `UVoxelSettings` (the season owns all three when assigned); radius 0 preserves the unbounded field. |
 | **`GetDensityAt`** | 218 | **Entry point.** Picks strate + generator type, materialises a cooked-season recipe on the existing per-chunk refetch when present, dispatches, then adds disturbances/diff. Its `CP_*` state is keyed by `(DensityCacheOwnerId, ChunkCoord, LayoutVersion)`; workers copy immutable recipe/vector data and never read editor composer state. |
-| **`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. |
+| **`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. The optional `voxel.WormBlockSkip` path uses `VF_TryGetWormBlockSkip` + a worker-local 4³ lattice-block cache to prove `|N1| >= WormThreshold` and remove both worm noise calls only; it never changes `NetworkMask` or the fallback field path. |
 | **`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. The field-preserving LOD0 pass removes only needless temporaries/default construction; every output remains bit-identical. §8.14. |
@@ -359,7 +359,11 @@ This is **where terrain shape lives.**
 > memoizes the strate index per (chunkZ, `GetLayoutVersion()`); `thread_local` per-cell lattice
 > bakes cover slab columns (`GetSlabDensity` step 4), maze open edges, vertical shafts +
 > cross-connectors, floating-island constants, and the disturbance chasms/bridges/ridges; worm
-> tunnels short-circuit the 2nd Perlin when N1 ≥ WormThreshold (N2 ≥ 0 ⇒ can't carve). Room
+> tunnels short-circuit the 2nd Perlin when N1 ≥ WormThreshold (N2 ≥ 0 ⇒ can't carve). With
+> `voxel.WormBlockSkip=1`, a worker-local cache proves whole 4³ lattice blocks only when the
+> actual 3D Perlin bound (`L = 8.118988160`, including `VOXEL_NOISE_SCALE`) plus a `1e-3`
+> output-rounding margin clears the threshold; failed proofs use the original per-sample path.
+> Room
 > shapes are pre-baked in `FCachedRoom` (§3.7). **T2.b:** per-voxel fractal call sites take their
 > octave count through `VoxelGenLOD::Eff(N)` (VoxelGenerator.h) — a `thread_local` bias set per
 > tile by the mesher drops tail octaves on coarse tiles (opt-in `LODOctaveDrop`, default 0 = off);