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

ARCHITECTURE.md

@@ -11,6 +11,50 @@
 A large A-to-Z expansion. The world is a stack of strates the player descends through;
 each strate can be a fundamentally different *archetype*, connected at (0,0).
 
+### 8.0 Human-scale generation contract (2026-09-05)
+
+All authored lengths are voxel-space values, converted at the boundary by `0.25 m/voxel`. The body
+reference is a **0.34 m radius, 1.76 m tall** capsule (`1.36 × 7.04` voxels). The default strate
+height is now **8 chunks = 256 voxels = 64 m**, which is intentionally larger than the 3-4 chunk
+boss-arena anchor so an archetype can reserve seals, vertical play, and a high ceiling together.
+
+The default size families are deliberately independent:
+
+| Feature | Default metre derivation | Coupling kept sound |
+|---------|--------------------------|---------------------|
+| Room network | radius 4-10 m (8-20 m diameters), origin radius 12 m (24 m hub), cell spacing 32 m | `MaxRoomRadius 40 < RoomSpacing/2 64`; a 6 m radial margin remains around the largest room |
+| Round passages | 1.5-2 m radius (3-4 m bores); maze corridor radius 2 m (4 m bore) | a 1.76 m body fits vertically with headroom; Maze `8 < CellSize/2 32` |
+| Slab | floor at 16 m, ceiling at 38.4 m, 22.4 m open span | floor/ceiling noise and 4-8 m column diameters remain inside the open span |
+| SurfaceWorld | 20 m terrain relief, 12 m warp, 60.8 m sky cap | terrain features are bounded below the 64 m strate envelope |
+| VerticalShafts | 4-7 m shaft diameters, 3 m connector bore, 8 m ledge interval | shaft spacing is 20 m; connector/ledge values are derived from the roughness envelope |
+| FloatingIslands | 12-24 m island diameters, 28 m cell spacing | the largest island leaves a 2 m centre-to-edge gap; thickness is separately derived |
+| Inter-strate passages | 3-4 m mouth bore, 3 m mid bore, 8-24 m reach, 16-48 m offset | width, reach, and wander are separate body/placement decisions |
+
+For wall detail, `VOXEL_NOISE_SCALE=1.25` and the proven `sup|fBM|=1.5` give a roughness reach of
+`1.875 × SurfaceRoughness` voxels. The default ratios are **0.625** against the minimum tunnel
+radius, **0.469** against the Maze corridor radius, **0.469/0.625** against shaft/connector radii,
+**0.234** against the minimum island radius (**0.484** including its 6-voxel blend), and
+**0.625/0.938** against slab column radius for floor/ceiling roughness. SurfaceWorld is a
+heightfield, so its **0.047** ratio is against its 80-voxel relief scale, not a fictitious radial
+feature. FlatPlain and CrystalChamber intentionally share `GetSlabDensity` and the same slab
+parameter block; they cannot acquire separate scale geometry without a generator change.
+
+This scale contract is informed by [Epic's Unreal level-blockout guidance](https://dev.epicgames.com/documentation/en-us/unreal-engine/designer-01-project-setup-and-level-blockout-in-unreal-engine), which recommends a player-sized reference and gives 2-3 m hall / 3-4 m height starting guidance. The
+[2010 ADA Standards](https://www.ada.gov/law-and-regs/design-standards/2010-stds/) are a lower-bound
+accessibility reference (915 mm clear walking width and larger passing/turning spaces), while
+[NPS Lehman Cave dimensions](https://www.nps.gov/grba/learn/nature/lehman-caves-dimensions.htm) support
+keeping natural chambers heterogeneous and allowing 20 m-plus cathedral volumes.
+
+Validation is deliberately split by cost: bounded regression fixtures remain 4 chunks, while the
+production definition, season defaults, and owner-facing showcase use 8 chunks. The final focused
+showcase (`WorldScaleShowcaseProductionFinal`) exhausted 256 rolls, measured 82 eligible single-region
+rolls, skipped 174 multi-region rolls while lateral regions remain gated, and found **0/8** complete
+hard-gate survivor set at fine step 1. It still produced diagnostic cards (7 fine renders, 1 refusal,
+1 blank). The full `VoxelForge` run (`WorldScaleFullFinal3`) recorded **28 successes, 2 warning-only,
+0 failures, 0 not-run**; all box-verdict violation counts were **0**, `WorldRadiusVoxels` stayed **0**,
+and operator-stack equivalence paths remained bit-identical. The two authored-corpus relation findings
+(2/12) are conservative experiment-envelope findings, not box-verdict violations.
+
 ### 8.1 Archetypes (`ECaveGeneratorType`, VoxelStrateTypes.h)
 Each archetype has its own param `USTRUCT` (on `UVoxelStrateDefinition`, EditCondition-gated
 by `GeneratorType`) and its own density function in `VoxelGenerator.cpp`, dispatched by the
@@ -421,7 +465,8 @@ TunnelNetwork and Underwater keep the nearest hash-room vertical placement at th
 `MakeStrateSeed(world-seed, strate-index)` matching the room graph's existing identity; FlatPlain and
 CrystalChamber recompute their slab void band and reject column-overlap points. Maze snaps to the
 nearest roughness-safe horizontal lattice corridor within one cell, VerticalShafts to the exact
-axis of a roughness-safe shaft on the drainage tree within one shaft spacing, and FloatingIslands
+axis of a roughness-safe shaft on the drainage tree within two shaft spacings at the default site
+density, and FloatingIslands
 to a validated blob top within one island spacing.
 Those three return false when no footing exists inside that explicit lateral budget. GeneratePassages
 interpolates the snapped XY through the control-point chain and recomputes its conservative bound;