R-14: look pack — AO, bevel, palette v2, --bare, capacity

[mrtlvmbt]

Summary

R-14 visual centerpiece: toy-diorama hex terrain with soft AO, subtle bevel, palette v2 two-factor coloring, and per-kind capacity management.

What landed

• Palette v2: two-factor color = material HUE × height VALUE + per-column jitter

  • Covers ALL material bytes 0–10 (added SoilDry/SoilWet)
  • Deterministic per-column ±4% variation via integer hash

• Per-vertex AO: baked into vertex colors at mesh build

  • Darkens top-face corners by count/height of strictly-higher neighbors
  • No shader changes; works identically on both render paths

• Top bevel: chamfer ring on hex prisms (~12 tris/cell)

  • Shrink top hexagon by BEVEL_FRAC (0.12), emit 6 chamfer quads
  • Slightly tilted normals for light catch

• Bare mode (--bare): water renders as dry-bed sand

• Capacity management: per-kind VERTS_PER_CELL_MAX + hard asserts

  • Hex: ~54 verts/cell → ~1111 cells per chunk at 60k soft budget
  • Hard asserts at build: chunk_verts < 60_000 && chunk_indices < 120_000

Acceptance status

• ✓ Compile: PASS (scripts/compile-check.sh from v2/crates/render)
• ✓ Both render paths updated (macroquad + retained GPU buffers)
• ⏳ Screenshot verification: PENDING (local cargo run blocked by no-local-sim guard)
• ⏳ HEIGHT_SCALE variants: 0.2/0.3/0.4 screenshots for user to pick

Code changes

biome_palette.rs

• Added materials 9, 10 (SoilDry, SoilWet)
• Implemented surface_color_v2(): two-factor palette with integer hash jitter
• Added color_jitter_hash()

terrain.rs

• Added BEVEL_FRAC, VERTS_PER_CELL_MAX constants
• Implemented calculate_vertex_ao(): per-corner AO calculation
• build_hex_terrain(): accepts seed, bare_mode parameters
• build_chunk(): bakes AO into top-face vertices, emits bevel quads (6 per cell)
• Hard capacity asserts (60k verts / 120k indices)

terrain_cube.rs

• Updated signatures for seed, bare_mode parameters
• Updated color calculation to use surface_color_v2()
• Updated test calls

main.rs

• Added --bare and --height-scale CLI flags
• Updated all terrain build calls to pass seed + bare_mode

Closes #440