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/layer_proxy.rs

@@ -95,21 +95,34 @@ pub fn handle_atlas_request(
     // Miss — resolve the source heightmap and enqueue background analysis.
     match resolver.resolve(&req.body_id) {
         Ok(heightmap_path) => {
-            // Pre-resolve this body's settlements so the Rayon work item stays
-            // DB-free (#955, D-225). A read failure is non-fatal: log and place
-            // no cities (Layer 1 still runs).
-            let cities = match city_reader {
-                Some(reader) => reader
-                    .read_body_settlements(&req.body_id)
-                    .unwrap_or_else(|e| {
-                        tracing::warn!(
-                            body_id = %req.body_id,
-                            error = %e,
-                            "settlement read failed; placing no cities"
-                        );
-                        Vec::new()
-                    }),
-                None => Vec::new(),
+            // Pre-resolve this body's settlements + system faction so the Rayon
+            // work item stays DB-free (#955/#956, D-225). Read failures are
+            // non-fatal: log and fall back (no cities / no faction → frontier).
+            let (cities, dominant_faction) = match city_reader {
+                Some(reader) => {
+                    let cities = reader
+                        .read_body_settlements(&req.body_id)
+                        .unwrap_or_else(|e| {
+                            tracing::warn!(
+                                body_id = %req.body_id,
+                                error = %e,
+                                "settlement read failed; placing no cities"
+                            );
+                            Vec::new()
+                        });
+                    let faction = reader
+                        .read_body_dominant_faction(&req.body_id)
+                        .unwrap_or_else(|e| {
+                            tracing::warn!(
+                                body_id = %req.body_id,
+                                error = %e,
+                                "dominant_faction read failed; defaulting to frontier"
+                            );
+                            None
+                        });
+                    (cities, faction)
+                }
+                None => (Vec::new(), None),
             };
             queue.submit(
                 GenWorkItem::AnalyzeBody {
@@ -118,6 +131,7 @@ pub fn handle_atlas_request(
                     sea_level: DEFAULT_SEA_LEVEL,
                     body_seed: SeedChain::for_body(world_seed, &req.body_id),
                     cities,
+                    dominant_faction,
                 },
                 GenPriority::Immediate,
             );