epic: worldmap procgen production pass

[zgeoff]

Production re-implementation of everything the biome procgen spike proved, per its harvest notes — the spike branch is reference material and never merges.

Scope

• worldmap: canonize lattice jitter 0.4 and the widened edge cap #875 lattice jitter canon
• worldmap-core: procgen hash/noise API and edge ownership shape #876 worldmap-core procgen API and edge ownership shape
• worldmap dev tooling: perf HUD, layer toggles, pan benchmark #877 dev tooling: perf HUD, toggles, pan benchmark
• stream world-map chunks incrementally with progressive builds #878 incremental chunk streaming
• render biome ground: relief, tint field, and grime #879 biome ground: relief, tint, grime
• scatter grammar: wilderness and debris behind a kit-piece interface #880 scatter grammar behind a kit-piece interface
• journeys layer: viaducts and edge furniture #881 journeys: viaducts and edge furniture
• places layer: node foundations, compounds, and archetype structures #882 places: node sites and archetypes
• landmark light pillars and blackout districts #883 light pillars and blackout districts
• spike: parametric kit pipeline and one-biome kitbash test #874 spike: parametric kit pipeline (exploration)
• design: worldmap visual identity — biomes, roads, fidelity targets #873 design: worldmap visual identity (discussion)

Notes

• Spec: https://github.com/zgeoff/vers/blob/spike/biome-scatter-grammar/HARVEST.md
• Parent exploration epic: implement initial worldmap exploration #110
• Rough order: 875/876/877 first (independent), 878 next, 879–883 on top; 874/873 run beside as the design track