Phase 2 of the D-243 re-scale. The ~1km carrier is renamed and re-scaled to
the 2km district, and every consumer reads scale from the canonical scale.rs
instead of a local literal.
- region_profile.rs -> district_profile.rs; RegionProfile -> DistrictProfile,
RegionPos -> DistrictPos (re-exported from scale::DistrictPos), derive_*_regions
-> derive_*_districts, across all 10 consumers + the derivation harness.
- chunk_context now references scale:: for the carrier cell: district 1024m -> 2048m,
shift 4 -> 5 (CHUNK_DISTRICT_SHIFT). This caught a real latent bug: the seed-district
index used a literal '>> 4' while the anchor used the constant, so same-district
chunks could derive different anchors — now both use scale::CHUNK_DISTRICT_SHIFT.
- derivation_harness scale literals ('>> 4', '* 1024', '0..16') converted to
scale:: constants (the same drift the canonical source eliminates). Believability
tests pass at 2km; the voxel determinism golden re-pinned (anchors moved with the
re-scale — deterministic, intended).
Full suite + clippy --all-targets -D warnings green. The district DERIVATION still
tiles the heightmap at 8 cells (the old coarse path); replacing it with on-demand
heightmap interpolation + detail-scatter is phase 3.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8
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