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/atlas/attractor_matching.rs

@@ -17,6 +17,7 @@
 
 use tracing::{error, warn};
 
+use crate::atlas::features::NO_WATER_BEARING;
 use crate::seed::{splitmix64, SeedChain};
 use crate::simulation::generator::{
     AttractorType, CompatibilityMatrix, GeographicAttractor, SettlementClass, SubBiomeVariant,
@@ -265,6 +266,7 @@ fn synthetic_attractor(placed: &[CityPlacement], grid_w: u32, grid_h: u32) -> Ge
         strength: 50,
         sub_biome: SubBiomeVariant::TemperateGrassland,
         terrain_modification_cost: 100,
+        water_bearing: NO_WATER_BEARING, // inland synthetic — no water direction
     }
 }
 
@@ -282,6 +284,7 @@ fn synthetic_attractor(placed: &[CityPlacement], grid_w: u32, grid_h: u32) -> Ge
 /// grids vary per seed (D-213) while staying deterministic (D-010).
 fn city_character(
     attractor_type: AttractorType,
+    water_bearing: u16,
     economic_role: &str,
     territorial_status: &TerritorialStatus,
     city_id: u64,
@@ -290,9 +293,15 @@ fn city_character(
     let archetype = political_archetype(territorial_status, economic_role);
     let pattern = arrangement_pattern(&archetype, economic_role);
     let free_bearing = (splitmix64(seed.seed() ^ city_id) % 360) as u16;
-    // river_bearing / coastal_facing are 0 until Layer 1 exposes terrain bearings
-    // (D-209 follow-on); free_bearing seeds the pioneer/open-terrain case.
-    let orientation = founding_orientation(&attractor_type, territorial_status, 0, 0, free_bearing);
+    // Layer-1 water bearing (#957) drives both the coastal facing and the river
+    // bearing (the anchoring attractor's direction-to-water); 360 = none → 0.
+    let wb = if water_bearing >= 360 {
+        0
+    } else {
+        water_bearing
+    };
+    let orientation =
+        founding_orientation(&attractor_type, territorial_status, wb, wb, free_bearing);
     (archetype, pattern, orientation)
 }
 
@@ -354,6 +363,7 @@ pub fn match_cities(
             flag_mismatch(&cities[ci].name, score);
             let (archetype, pattern, orientation) = city_character(
                 attractors[ai].attractor_type,
+                attractors[ai].water_bearing,
                 &cities[ci].economic_role,
                 territorial_status,
                 cities[ci].city_id,
@@ -420,6 +430,7 @@ pub fn match_cities(
             flag_mismatch(&cities[ci].name, score);
             let (archetype, pattern, orientation) = city_character(
                 attractors[ai].attractor_type,
+                attractors[ai].water_bearing,
                 &cities[ci].economic_role,
                 territorial_status,
                 cities[ci].city_id,
@@ -453,6 +464,7 @@ pub fn match_cities(
         flag_mismatch(&city.name, score);
         let (archetype, pattern, orientation) = city_character(
             AttractorType::PlainCenter,
+            synthetic.water_bearing,
             &city.economic_role,
             territorial_status,
             city.city_id,
@@ -659,6 +671,7 @@ mod tests {
             strength,
             sub_biome: SubBiomeVariant::TemperateGrassland,
             terrain_modification_cost: 100,
+            water_bearing: NO_WATER_BEARING,
         }
     }