feat(simulation): D-232 three-phase trait draw + deviation/swerve system (T-994, T-1003)

T-994 — three-phase draw replacing the flat splitmix64 flavor pick:
- Phase 1 body K-draw (trait_draw.rs): hard gates -> soft weights (two-part
  geographic_sector join, PR #148) -> SeedChain::for_body-seeded weighted
  draw of K (5/3/1/0 by ComplexityTier), pins count toward K, coverage-aware
  over a new body-level district-type-mix aggregate threaded into
  CityGenerationContext at L3->L4 dispatch.
- Phase 2 district-dominant pick keyed by the D-243 2048m District cell —
  settlements sharing a cell independently derive the identical template.
  Resolved at dispatch, never in FillChunk (T-987 stays pure).
- trait_catalog_reader.rs: systems.db reader for trait_templates +
  atlas_body_trait_bias (D-225 resource pattern), registered in main.rs
  with graceful degradation.
- BlockSkeleton carries district_type; assign_block_tags is a pure lookup.

T-1003 — deviation/swerve system (trait_swerve.rs):
- ArchitectureFlavorRef is now InVocabulary(u8) | Swerve(tag).
- Rare per-building wildcard: foreign-import pool (other corridors +
  cross_corridor) driven by Epicenter/Passage tier, mixed faction,
  road-graph degree; heritage-callback pool (own-corridor heritage) driven
  by isolation, remote tier, founding_age_years. Integer bps, base 100,
  cap 300 per driver — placeholder constants pending calibration.
- Sparsity escape hatch = same mechanism, necessity-triggered at the
  phase-2 pick (deterministic max-weight over the hard-gate-eligible pool).
- New SeedDomains: TraitVocabulary(13) / TraitDistrict(14) / TraitSwerve(15).

Governance: D-232 amended (district pinned to the D-243 2048m tier — the
D-222/D-243 redefinition was never captured; swerve driver mappings +
placeholder rates recorded), D-229 flavor_ref field updated to the enum
shape, D-235 amended (T-995 vocabulary ratification note; rides here due
to single-file entanglement).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/seed.rs

@@ -120,6 +120,22 @@ pub enum SeedDomain {
     /// keyed by a single constant id). Distinct domain so the mosaic-selection lattice
     /// can never correlate with the relief, cover, or per-voxel terrain streams.
     VoxelMosaic = 12,
+    /// Architecture-flavor body-vocabulary K-draw (D-232 phase 1, T-994). Keyed by
+    /// a constant id (one draw per body — `SeedChain::for_body` already isolates
+    /// bodies). Distinct domain so the vocabulary draw can never correlate with
+    /// any other body-scoped stream.
+    TraitVocabulary = 13,
+    /// Architecture-flavor district-dominant template pick (D-232 phase 2, T-994).
+    /// Keyed by a packed `(DistrictPos, DistrictType)` id so every settlement whose
+    /// quarter falls in the same D-243 2 048 m district independently derives the
+    /// *identical* dominant template for a given district type — same body seed +
+    /// same key, no cross-quarter coordination required.
+    TraitDistrict = 14,
+    /// Per-building deviation/swerve roll (D-232 deviation system, T-1003).
+    /// Derived off the footprint's own chain, keyed by footprint index. Distinct
+    /// domain so the rare-wildcard roll can never correlate with the zone/era/
+    /// extent draws sharing that chain.
+    TraitSwerve = 15,
 }
 
 /// A position in the deterministic seed tree (D-224).
@@ -281,6 +297,9 @@ mod tests {
         assert_eq!(SeedDomain::Cover as u64, 10);
         assert_eq!(SeedDomain::VoxelRelief as u64, 11);
         assert_eq!(SeedDomain::VoxelMosaic as u64, 12);
+        assert_eq!(SeedDomain::TraitVocabulary as u64, 13);
+        assert_eq!(SeedDomain::TraitDistrict as u64, 14);
+        assert_eq!(SeedDomain::TraitSwerve as u64, 15);
     }
 
     #[test]