perf(opstack): direct-indexed column box (measured 14.7% miss); + T1.d bail attribution

BUILD RESULTS FIRST: 14/14 tests green, 0 violations. VerticalShafts box
verdicts went 0 -> 30 of 60 (zero was the number for the project's whole life).
TunnelNetwork production held at 11 proved / 14641 voxels, byte-identical --
that line was the isolated diagnostic for cab8e8f, so its stillness proves
Jahni's room/tunnel Min <= Max are correctly ordered. All eight equivalence
tests bit-identical, which TESTS the "bounds only, cannot reach density" claim
made on 7dbdf51 / eaa44bf / cab8e8f rather than asserting it.

PART A -- the column memo thrash is confirmed quantitatively. Measured 14.74%
miss rate against a prediction of 14.0% if thrashing and 1.4% if not; and 8,300
recomputes per tile against a healthy 1,225 (6.8x) from an independent
statistic. Replaced the 4096-slot direct-mapped hashed table with the
direct-indexed box scheme GSurfColCache has always used: no hash, no
collisions, every column computed exactly once. ParamsFingerprint is retained
in the box key -- its absence was the shipped bug that silently deleted the
overhang, and GSurfColCache's own omission of it was deliberately not copied.

PART B -- T1.d never fires in game: the two op-stack counters never appeared,
and since every displayed row has Min 1.00 rather than 0.00, rows only render
when a counter fires. The cave branch has 13 return-Mixed paths; guessing which
is the mistake this project keeps paying for. Six attribution counters now name
the bail category outright. Only edits there are brace-expansions so a counter
fits before each existing return -- every condition and returned value is
byte-identical.

Open falsifiable hypothesis: Tiles Meshed averages 2.13/frame, plausibly the
reason LOD rings update slowly. If misses drop ~10x and LODs speed up, the memo
was the ceiling; if not, they are separate problems, cleanly separated.

Not built -- Jahni builds.

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

CODEMAP.md

@@ -79,7 +79,7 @@ Paths relative to `Source/VoxelForge/`. `Public/` = headers, `Private/` = impl.
 | `../../VoxelForge.uplugin` | Plugin manifest. One Runtime module `VoxelForge`. Beta. |
 | `VoxelForge.Build.cs` | Deps: Core, CoreUObject, Engine, **GameplayTags**, **RealtimeMeshComponent**. |
 | `Public/VoxelForgeModule.h` / `Private/VoxelForgeModule.cpp` | `FVoxelForgeModule` boilerplate (Startup/Shutdown just log). |
-| `Public/VoxelStats.h` / `Private/VoxelStats.cpp` | `stat VoxelForge` DWORD counters for tile classification, skipping, meshing, and operator-stack verdicts. |
+| `Public/VoxelStats.h` / `Private/VoxelStats.cpp` | `stat VoxelForge` DWORD counters for tile classification, skipping, meshing, operator-stack verdicts, and cave-bail diagnosis. |
 
 ### 3.2 Foundational types — `Public/VoxelTypes.h` (no UClass, everyone includes it)
 | Symbol | Line | Notes |