wip(unreal): round 3 -- owner's in-game defects classified; opening room fixed; Core biome query

Luna, integration round 3, from the owner's four in-game screenshots:
- Capsule rings at the opening and the shaft continuing through the cave room were Core
  world defects: the synthetic bore is removed and the opening gets a finite origin room
  and floor (solid below). New world version, W1/W8/W16 identical: density
  a8bcb72d41092503, mesh 90f29ba15e24579f, payload 82c6b489e7bb7fd7, topology
  7b99448a1f844f2c.
- B-side landing and surface: headless coverage found no missing tiles or LOD-transition
  gaps (960 / 640 fine tiles compiled after travel); best explained by Core's missing
  SurfaceWorld representation. Null-RHI cannot rule out a presentation-only issue.
- Core mode GetBiomeAtWorldLocation now answers (e.g. Biome_Surface_Plain); biome
  terrain itself is not generated yet (proposal: native Core SurfaceWorld evaluator).
Owner checked the Step29 viewer himself: the surface strate type is absent there too.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

CLAUDE.md

@@ -25,10 +25,15 @@ try to run anything.
 ## Hard rules (these prevent real bugs — verify against code, don't assume)
 - **Density sign: negative = solid, positive = air** (MC convention at the mesher).
   `FVoxelModification::Strength` negative = carve. *The #1 source of confusion.*
-- **Density functions take VOXEL coords, not cm.** One voxel is 12.5 cm; one 32³ chunk is 4 m.
-  Conversions live in `VoxelTypes.h`.
+- **Density functions take VOXEL coords, not cm.** The legacy plugin field uses 12.5 cm voxels;
+  the opt-in Core field uses 25 cm voxels and its own tile keys. One legacy 32³ chunk is 4 m.
+  Conversions live in `VoxelTypes.h` and the Core bridge; do not mix scales in queries, anchors, edits,
+  or surface lookups.
 - **Determinism:** all randomness = hash of (coord, seed, strateIndex). No RNG state — same seed ⇒
   same world. Player edits (diff layer) are the only non-deterministic overlay.
+- **Core world invariants:** Core density keeps the same sign (negative solid, positive air), but Core
+  voxel coordinates are 25 cm. Worker-count changes must preserve hashes; Core world edits are
+  intentional world-version changes and must retain finite, walkable strate entrances and exits.
 - **Async safety:** worker tasks only READ Generator/Mesher, must check `bShuttingDown`, and return via
   the result queues — `ProcessQueue` and its `CriticalProcessQueue` / `EditedProcessQueue` /
   `NearProcessQueue` siblings (all must stay `EQueueMode::Mpsc`). `EndPlay` blocks on `ActiveTaskCount → 0`.