feat(simulation): Layer-3 settlement spatial-character enrichment (#956)

Derive and store each placed settlement's spatial character on top of the
#955 placement (D-212/213/214/215). Derivation is pure + integer-deterministic
(D-010); the cascade stays DB-free (D-225) — the enqueuer pre-resolves the
body's system faction onto the work item, like #955's settlements.

- TerritorialStatus (D-212): mapped from the authored dominant_faction
  (territorial_status_from_faction). Adds an AutonomistHeld variant for the
  Compact of Westphalia (self-governing bloc that rejects Assembly authority —
  neither Commission, Corp, Contested, nor truly Frontier). Grounded in
  wiki/factions/. Stored per-province on DrainageBasin.territorial_status
  (uniform per body for now; forward-compatible for per-province faction data).
- PoliticalArchetype (D-214): political_archetype(status, role), status takes
  precedence over economic_role.
- ArrangementPattern (D-215): new 5-variant enum + arrangement_pattern(); the
  block-adjacency *enforcement* stays deferred to the Quarter-skeleton gen (#957)
  — this only derives + stores which pattern applies.
- FoundingOrientation (D-213): existing fn extended with a seed-derived Free
  bearing so pioneer/open-terrain grids vary per seed.

Wiring: dominant_faction threaded through CityContextReader
(read_body_dominant_faction) → atlas proxy (cache-miss read) → AnalyzeBody work
item → run_cascade → run_layer3/match_cities. Enrichment stored on CityPlacement
(political_archetype, arrangement_pattern, founding_orientation).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/src/atlas/plugin.rs

@@ -161,6 +161,7 @@ mod tests {
                 sea_level: 0.3,
                 body_seed: SeedChain::for_body(42, "PlanetX"),
                 cities: vec![],
+                dominant_faction: None,
             },
             GenPriority::Immediate,
         );