test(simulation): rebake golden + atlas fixture for Layer-3 enrichment (#956)

DrainageBasin gained a territorial_status field, so the Layer-1 golden and the
atlas_response msgpack fixture pick it up. Both changes are additive/
representational — basin/attractor/river selection is unchanged.

- cascade_golden.rs: pass None dominant_faction; golden rebaked (only
  "territorial_status": "FrontierUnclaimed" added per basin).
- gen_fixtures.rs: set the new field in the atlas_response generator; fixture
  regenerated.

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

server/tests/cascade_golden.rs

@@ -55,7 +55,8 @@ fn cascade_layer0_to_1_matches_golden() {
     // ── Layer 1 — downsample, then run the cascade to topography. ───────────
     let small = heightmap.downsample(DOWNSAMPLE.0, DOWNSAMPLE.1);
     let body_seed = SeedChain::for_body(WORLD_SEED, "GJ1c");
-    let snapshot = run_cascade_from_heightmap(body_seed, small, &[], CascadeLayer::Topography);
+    let snapshot =
+        run_cascade_from_heightmap(body_seed, small, &[], None, CascadeLayer::Topography);
     let layer1 = snapshot.layer1.expect("Layer 1 ran");
 
     let actual = json!({

server/tests/gen_fixtures.rs

@@ -553,6 +553,8 @@ fn generate_atlas_layer_response_fixtures() {
             basin_id: 1,
             boundary: vec![(0, 0), (0, 10), (10, 10), (10, 0)],
             area_pct: 0.42,
+            territorial_status:
+                settled_reach_server::simulation::generator::TerritorialStatus::FrontierUnclaimed,
         }],
         attractors: vec![GeographicAttractor {
             position: (12, 58),

server/tests/golden/cascade_layer1.json

@@ -6380,7 +6380,8 @@
             1,
             0
           ]
-        ]
+        ],
+        "territorial_status": "FrontierUnclaimed"
       },
       {
         "area_pct": 0.02642822265625,
@@ -6806,7 +6807,8 @@
             69,
             93
           ]
-        ]
+        ],
+        "territorial_status": "FrontierUnclaimed"
       },
       {
         "area_pct": 0.05499267578125,
@@ -7448,7 +7450,8 @@
             84,
             197
           ]
-        ]
+        ],
+        "territorial_status": "FrontierUnclaimed"
       },
       {
         "area_pct": 0.02691650390625,
@@ -7498,7 +7501,8 @@
             92,
             0
           ]
-        ]
+        ],
+        "territorial_status": "FrontierUnclaimed"
       }
     ],
     "grid_h": 128,