Harden RC7 API response contracts

backend/tests/test_sprint219_regional_raster_explorer.py

@@ -8,12 +8,12 @@ def test_partitioned_raster_routes_are_canonical_and_documented() -> None:
     routes = (ROOT / "backend/app/api/routes/datasets.py").read_text(encoding="utf-8")
     contracts = (ROOT / "docs/API_CONTRACTS.md").read_text(encoding="utf-8")
 
-    for path in (
-        "/datasets/raster/terrain/select",
-        "/datasets/raster/flood-hazard/select",
-    ):
-        assert f'@router.post("{path}", response_model=dict)' in routes
-        assert path in contracts
+    assert '"/datasets/raster/terrain/select",' in routes
+    assert "response_model=Envelope[TerrainSelectionResponse]" in routes
+    assert '"/datasets/raster/flood-hazard/select",' in routes
+    assert "response_model=Envelope[FloodHazardSelectionResponse]" in routes
+    assert "/datasets/raster/terrain/select" in contracts
+    assert "/datasets/raster/flood-hazard/select" in contracts
     assert "envelope(TerrainAnalysisService.analyze_partitions" in routes
     assert "envelope(FloodHazardAnalysisService.analyze_partitions" in routes