perf(opstack): retain six surface column regions

The single direct-indexed box discarded all 6,561 computed columns whenever spatial or column identity moved. Port the reference six-box LRU so interleaved regions keep five warm working sets, accepting the documented ~0.79 MiB TLS cost per worker to preserve the recommended and measurable A/B path. Also report disabled cave opt-ins at layout initialization; SurfaceWorld is excluded because its exact-lattice tile proof does not use that flag.

CODEMAP.md

@@ -152,7 +152,7 @@ bit. They are port-correctness oracles, not fidelity checks: the acceptance bar
 | `VoxelDensityOps::MakeSlabVoidSource` | 1 | Floor surface + ceiling surface → void field. **XY-pure** since §3.1, which is what gives it an **exact `ClassifyBox` with no sampling**: FBM's `[-1,1]` contract bounds both surfaces into known Z bands. Serves FlatPlain **and** CrystalChamber. |
 | `VoxelDensityOps::MakeGridColumnMod` | 3 | Infinite-height cylinders on a world grid, 3×3 cell memo. Adds solid only ⇒ `FillOnly` when a column reaches the box, `Identity` otherwise — and that `Identity` is what lets the source's `AllAir` verdict survive. |
 | `VoxelDensityOps::BuildSlabStack` | — | 5 ops, **no branch on archetype**: FlatPlain and CrystalChamber differ only in defaults, exactly as `GetSlabDensity` already had it. 8 archetypes → 7. |
-| `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`. |
+| `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 a **six-box spatial LRU** of direct-indexed per-column cells, keyed by `PrepareChunk` on `(StrateBottomWorldZ, LayoutVersion, Seed, ParamsFingerprint)` so it is **shared down the whole vertical strate stack**, exactly like `GSurfColCache`. Six 81×81 boxes preserve hot columns across interleaved regions at roughly 0.79 MiB TLS before padding (more memory, fewer whole-cache recenter/recompute misses). Fractional XY remains direct-compute. |
 | `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 — this is the T1.d switch (measured: **6 of 40 tiles proved AllSolid at production defaults, 7986 voxels brute-forced, 0 violations**). It builds the cache for the queried box into a *second* per-worker cache (never `FState::Cache`), then applies a **disjunction** per primitive: it doesn't matter if it **fails its cull** *or* if **its own SDF stays ≥ `T+K`** over the box. Cull wins for rooms (`Rmax+3K` < `Rmax+T+K`); the threshold wins hugely for tunnels, whose cull is a capsule *bounding sphere* (~107 radius for a 200-long tube of radius 7). ⚠️ **`Identity` therefore means `Sdf ≥ T`, not `Sdf == FLT_MAX`**, with `T = max(3·SDFBlendRadius, WormNetworkRange)` — **any new consumer of the `Sdf` channel must have a threshold ≤ T or be added to that max**, or it gets tiles with no geometry and no collision. The `−K` slack covers any number of primitives because `SmoothMin`'s penalty is exactly 0 once `\|A−B\| ≥ K`. Pits/chimneys use the cull only; columns are **not** tested (their sole consumer gates on `Sdf`, so the test was redundant). Verdict memoised per box; warp dilation uses a **provable** `\|Perlin3D\| ≤ 2`. |
@@ -338,7 +338,7 @@ Maps depth→strate at runtime; owns passages.
 - `FStrateSlot` (h:84): definition + chunk-Z range + index.
 | Method | .cpp line | Role |
 |--------|-----------|------|
-| `Initialize` | 10 | Builds the stacked layout from settings+seed (fixed slots + shuffled pool), then `GeneratePassages`. |
+| `Initialize` | 10 | Builds the stacked layout from settings+seed (fixed slots + shuffled pool), logs every **cave** slot whose operator-stack opt-in is disabled, then `GeneratePassages`. SurfaceWorld is deliberately excluded from that diagnostic because its exact-lattice T1.d path does not depend on the flag. |
 | `GeneratePassages` | 146 | Deterministic passages between consecutive strates (per-type control points). |
 | `EvaluateModifierSDF` | 357 | SDF of passages at a point (for carving). Per-chunk `thread_local` shortlist (`PassagesVersion`-stamped) → far chunks return `FLT_MAX` without walking `Passages`. §8.10. |
 | `AnyPassageNearBox` | — | Conservative sphere-vs-AABB test of every passage's bound against a voxel box (+carve blend pad). Per TILE (ClassifyTile guard), never per voxel. |