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/atlas/gen_queue.rs

@@ -578,6 +578,13 @@ mod tests {
                 trait_selection: vec![],
                 dominant_bulk_class: BulkClass::NonPhysical,
                 dominant_production_ubiquity: ProductionUbiquity::Common,
+                geographic_sector: None,
+                body_district_type_mix: vec![],
+                settlement_district_pos: (0, 0),
+                district_dominant_by_type: Default::default(),
+                swerve_rates_bps: (0, 0),
+                swerve_foreign_pool: vec![],
+                swerve_heritage_pool: vec![],
             }),
             quarter_id: city_id * 10,
             chain: SeedChain::root(42 + city_id),
@@ -710,7 +717,7 @@ mod tests {
                     heights: FloorHeightProfile::Uniform(3),
                 },
                 entry_class: BuildingEntryClass::Public,
-                flavor_ref: ArchitectureFlavorRef { flavor_index: 0 },
+                flavor_ref: ArchitectureFlavorRef::InVocabulary(0),
                 era: ConstructionEra::Founding,
                 era_cause: EraCause::Original,
                 initial_condition: TileCondition::Intact,