Add governed SPW bathymetry analysis

docs/API_CONTRACTS.md

@@ -2192,9 +2192,9 @@ sets an explicit Ollama context window and returns
 
 Returns the governed bathymetry source registry in the canonical envelope.
 VHA inland profiles are `operational`. MDK Belgian Continental Shelf is
-`probe_only`; SPW Walloon bathymetry remains `available_not_integrated`.
-Neither source can be acquired until its raster/download and vertical-datum
-flow passes live validation.
+`probe_only`. The pinned SPW Walloon bathymetry archive is `operational`
+through a bounded, explicit operator import. There is no browser-side source
+fetch and no arbitrary source URL.
 
 ### GET `/api/v1/projects/{project_id}/datasets/bathymetry/sources/mdk_bcp_bathymetry/readiness`
 
@@ -2261,6 +2261,31 @@ request limit, while `total_feature_count` and all configured depth/width
 metrics are calculated across the complete spatial result. Empty municipalities
 return an empty, honest result. No provider request occurs during analysis.
 
+### POST `/api/v1/projects/{project_id}/datasets/{dataset_id}/raster/bathymetry/select`
+
+Runs a bounded selection against a ready persisted
+`source_name=spw_bathymetry` raster. The request contains an EPSG:4326 bbox
+and optional persisted `area_id`, matching the other governed raster-selection
+contracts.
+
+The response reports:
+
+- mean, minimum, maximum, p10 and p90 waterbed elevation in `m mDNG`;
+- exact raster-cell surface with surveyed bed values in hectares;
+- source coverage percentage inside the selected geometry;
+- source resolution, survey period `2019-2022`, vertical reference and
+  explicit unsupported metrics.
+
+`current_water_depth_m`, `water_volume_m3` and vertical-datum conversion remain
+unsupported. The endpoint reads the persisted EPSG:3812 geometry-aligned
+raster; it does not query SPW and does not synthesize missing cells.
+
+### GET `/api/v1/projects/{project_id}/datasets/{dataset_id}/raster/bathymetry/image`
+
+Returns a transparent PNG rendering of the persisted bathymetry COG for the
+MapLibre image-overlay path. Rendering changes presentation only. Analytical
+values always come from the stored Float32 source cells.
+
 Future provider output continues to use DatasetService and, for vectors,
 VectorFeatureService. Arbitrary service URLs, browser-side fetches, insecure
 TLS bypasses and startup downloads remain forbidden.