Wire the existing attractor-matching engine (#919/#925) into the
generation cascade as Layer 3, and make the whole placement-scoring path
integer-deterministic.
Layer 3 (D-211):
- CascadeLayer::Settlement + Layer3Output (placements) on the snapshot;
BodyWorldState gains a `placements` field (the D-203 hot cache).
- run_layer3 runs the five-phase match_cities against Layer-1 attractors
via the authored D-195 compatibility matrix; pure function of
(attractors, cities) — no RNG. cities are passed in by the caller so the
cascade stays DB-free and testable. A `// cache seam` marks where a
persistent cache wraps it later (#1021).
- gen_queue passes &[] for now (Topography needs no cities); the runtime
settlement read (gen_queue/layer_proxy) is the #955 follow-on.
Integer determinism (D-010 / D-227 — D-195 amended):
- Wiring match_cities into the deterministic cascade made its f32 scoring
a live cross-platform divergence risk (a near-tie comparison or the
Hungarian's f32 reductions can round differently per platform → a
different world from the same seed). Converted the entire path to
integers: CompatibilityMatrix is a 0-100 affinity table; attractor
strength is 0-100 and terrain cost is a percent (100 = baseline),
quantized once at the Layer-1 feature boundary; cell_score, the
Hungarian, and CityPlacement.score are i64. No f32 in any placement or
ranking decision.
- Layer-1 golden fixture rebaked: confirmed selection/positions are
unchanged (same 256 attractors, 93 river cells) — only the strength/cost
representation changed.
Tests: lib green (1292); new settlement_layer_places_cities_deterministically
covers placement + determinism + propagation into BodyWorldState.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8
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