feat(scale): size the world to a human body -- and it is NOT enough

Jahni: "can't you try and make the world to scale?" Every length parameter
is now derived from the body and annotated with its metre value, so nobody
has to do the arithmetic to notice something is absurd.

  CorridorRadius   4 -> 8     1 m -> 2 m radius (4 m bore)
  CellSize        40 -> 64    keeps a real wall between wider corridors
  TunnelMinRadius  3 -> 6     0.75 m -> 1.5 m
  ShaftMinRadius   5 -> 8     1.25 m -> 2 m
  IslandMinRadius 18 -> 24    4.5 m -> 6 m
  MouthRadius      6 -> 8     passage mouths 4 m
  plus passage reach, spiral, cascade, bridges, ridges, chasms

The reasoning that motivated it still looks right: a 2 m circular bore for
a 1.76 m player clears the head only along the exact centreline, so almost
no cell has a floor with 7.04 voxels of clear air above it. A 4 m bore is
genuinely walkable.

⚠️ BUT IT DID NOT FIX TRAVERSABILITY, and this time it is not the
instrument. The player-fit law is measured at STEP 1 on a mouth-fitted
window -- full resolution, both mouths inside the box -- and across the
eight showcase archetypes it reports:

  6 NotConnectedAtThisResolution   (real negatives at full resolution)
  2 OutOfWindow                    (unmeasurable, not passing)
  1 StartCellNotPlayerFit          (the arrival mouth itself is too small)
  0 CONNECTED

And every archetype reports hard-gate survivors=0, so the showcase is
displaying the least-bad of an entirely failing set.

⛔ DO NOT READ player_fit_fraction / player_clearance FROM THE SHOWCASE
LINE. Those come from the COARSE step-4 measurement in the same log line,
where the 1.36-voxel player is sub-cell and fit is unmeasurable --
player_clearance reads a uniform "1.00 voxels" for all eight archetypes,
which is one cell, not one voxel. Only restricted_law is at step 1 and
only it is trustworthy. Fixing that mixed-resolution reporting is next.

So scale was necessary and insufficient. My hypothesis was that bore
diameter versus body height was the binding constraint; doubling it moved
nothing measurable. Something else is preventing player-sized volume from
existing at all -- worth finding before tuning any further.

Codex applied these edits and then died mid-poll without validating them
(third time a killed agent left a clean-looking unbuilt diff). Build and
suite run by me: build clean, 30 succeeded / 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K8V9my1PL68pmQb2gutZZV

Source/VoxelForge/Private/Tests/VoxelForgeTestFixture.h

@@ -73,7 +73,8 @@ namespace VoxelForgeTest
          * dangerous — and `VoxelForge.Determinism.LargeSeedSurvives` deliberately passes big ones
          * (up to 2e9) to prove it stays that way.
          */
-        void Build(int32 InSeed = 1337, int32 InGapChunks = 2, bool bUseOperatorStack = false)
+        void Build(int32 InSeed = 1337, int32 InGapChunks = 2, bool bUseOperatorStack = false,
+                   int32 InStrateHeightInChunks = 4)
         {
             Settings = TStrongObjectPtr<UVoxelSettings>(
                 NewObject<UVoxelSettings>(GetTransientPackage(), NAME_None, RF_Transient));
@@ -105,7 +106,11 @@ namespace VoxelForgeTest
                 UVoxelStrateDefinition* Def = NewObject<UVoxelStrateDefinition>(
                     GetTransientPackage(), NAME_None, RF_Transient);
                 Def->GeneratorType = Archetypes[i];
-                Def->StrateHeightInChunks = 4;
+                // Keep the shared density fixture at the historical 4-chunk test volume unless
+                // a caller explicitly asks for the production/default 8-chunk envelope. The
+                // refinement and roll tests use the smaller synthetic volume as a bounded memory
+                // control; the owner-facing showcase opts into 8 chunks below.
+                Def->StrateHeightInChunks = FMath::Max(1, InStrateHeightInChunks);
                 // L'OPT-IN de la pile d'opérateurs. Faux par défaut : les treize tests existants
                 // doivent continuer à exercer le `switch`, qui reste le comportement de référence.
                 // Seul le test de solidité de ClassifyTie côté pile le passe à vrai.