feat(simulation): Layer-1 water bearing + D-234 waterfront rule (#957)

Close the last D-234 piece — terrain water-direction extraction wired through
to founding orientation and the quarter waterfront rule:

- Layer 1: TerrainAnalysis::water_bearing — 8-octant integer bearing toward the
  nearest water from the water_dist gradient (D-010, no atan2). Stored on
  GeographicAttractor.water_bearing (360 = none).
- #956 founding orientation: coastal/river settlements now get a real
  water-facing bearing (the anchoring attractor's), replacing the 0 stub.
- #957 waterfront rule (D-234b): the water-facing quarter edge (from the
  settlement's Coastal founding orientation) drops its block setback to 0 so
  buildings present flush to the quay (dock-orthogonal). Typed Edge + coastal_edge
  + per-block gating.

Golden + atlas_response fixture rebaked (additive water_bearing field only).
8 new tests. All integer-deterministic (D-010).

Pending: the waterfront rule reads context.founding_orientation, which
city_context_reader still stubs to Cardinal — real per-settlement orientation
reaches quarter generation once the Layer-3 placement -> Layer-4 GenerateSkeleton
dispatch is wired (the remaining cross-layer integration).

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

server/src/simulation/generator.rs

@@ -529,6 +529,12 @@ pub struct GeographicAttractor {
     /// `sub_biome` + local slope; penalizes marginal cities in the matching
     /// pipeline (D-211). Integer for D-010 determinism (#955). (D-210)
     pub terrain_modification_cost: i32,
+    /// Compass bearing (degrees, quantized to 8 octants: 0=N,45=NE…315=NW)
+    /// toward the nearest water from this position, or 360 = "no water nearby".
+    /// Layer-1 terrain extraction feeding D-213 founding orientation (coastal
+    /// facing / river bearing) and the D-234 waterfront rule. Integer 8-octant
+    /// keeps it D-010-deterministic (no `atan2`).
+    pub water_bearing: u16,
 }
 
 /// Compatibility weights between economic roles and attractor types.