fix(opstack): the worm inherits the room source's box verdict -- the actual blocker

First build of the spatial EffectOverBox came back green with 0 tiles proved of
40. The warning written for exactly that case fired, and then was not good
enough: it offered two candidate causes and BOTH were wrong. The real one was a
third operator neither candidate mentioned.

FWormFieldSource answered CarveOnly unconditionally with a provably correct
amplitude bound of WormStrength. But BaseDensity = 8 and WormStrength = 10 are
the DEFAULTS -- the field's own comment requires the worm to exceed BaseDensity
or it could never carve air. So SolidMargin = 8 - 10 < 0 on every tile of every
strate with worms on, before the fold reached anything the room source proved. A
numerically correct bound that is structurally always fatal.

The fix was already written three lines up in the worm's own Eval: NetworkMask
is 0 when CaveSDF >= WormNetworkRange, which FLT_MAX always satisfies. The worm
IS spatially bounded -- by the room source's bound, exactly like the twelve
detail modifiers -- so where the source proves Identity it does not execute at
all. Thirteen inheritors instead of twelve. Verified FVoxelOpSample::Sdf really
does initialise to FLT_MAX rather than assuming it; the inheritance inverts into
a hole otherwise.

Deliberately NOT VF_NoCaveOverBox: that helper answers "identity" for a null
Rooms, correct for the twelve modifiers and wrong for an op a future assembly
could place behind a different SDF writer. No room source means we do not know,
which must cost CPU rather than a hole.

And the instrument, because the guess is the thing that cost a build: a
diagnostic that lists candidate causes without measuring them is still a guess
wearing rigour. FVoxelOpStack::ClassifyBoxAttributed reports the index of the
first op that kills each hypothesis -- same loop, same early-out, verdict
identical to ClassifyBox, because a diagnostic that takes a different path than
the thing it explains sends you hunting in the wrong place.
IVoxelDensityOp::DebugName gives them names and touches no cache key, so it
cannot change the world. Check 4 now always prints "AllSolid killed by: <op>
xN", and the zero-proved warning says to read it instead of re-deriving.

Unbuilt.

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

CODEMAP.md

@@ -155,7 +155,7 @@ bit. They are port-correctness oracles, not fidelity checks: the acceptance bar
 | `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**; 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. |
+| `FWormFieldSource` (internal) | 1 | Fielded 3D-noise threshold carve, masked by distance to the room network (reads `InOut.Sdf` *after* pits/chimneys). **`EffectOverBox` INHERITS `FRoomGraphSource`'s verdict** since 2026-07-28 — its `Eval` sets `NetworkMask = 0` when `CaveSDF >= WormNetworkRange`, which `FLT_MAX` always satisfies, so where the room source proves `Identity` the worm doesn't execute at all. ⚠️ This was **the** blocker: `BaseDensity = 8` < `WormStrength = 10` **by default** (the field comment requires it), so an unconditional `CarveOnly` drove `SolidMargin` negative on every tile in the world and no room-source proof could survive behind it. Deliberately **not** `VF_NoCaveOverBox` — that helper answers "identity" for a null `Rooms`, which is wrong for an op that could sit behind a different SDF writer. |
 | `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. |
 | `FCaveTerraceMod` (internal) | 3 | STEP 4c. The only modifier that **re-queries the SDF** (Z±1, through `FRoomGraphSource::ProbeSdfUnwarped`) for its horizontality gate — which is why the room source's cache is exposed at all. ⚠️ Those probes use unwarped X/Y and raw Z although the field was evaluated warped: transcribed as-is, see OPSTACK-PROGRESS. |