scope frontend contracts to the feature, not to one file

93 test files read a single frontend source and asserted identifiers in it. The
MapWorkspace split showed what that costs: 24 tests went red for a move that
changed no behaviour at all. A contract belongs to the feature — a container,
its hooks, its domain layer — not to whichever file currently holds it.

232 read sites now resolve through read_feature(). The distinction that makes
this safe is direction: a *positive* contract ("this is wired") may widen,
because the identifier must still exist somewhere in the feature; a *negative*
one ("this component performs no transport") is a statement about one file, and
widening it would quietly weaken the check. The 73 single-file reads that
remain are exactly those, and a guard now enforces the rule for new tests.

Verified rather than assumed: of the 732 migrated positive assertions, 644 still
match exactly one module — as specific as before — and the other 86 already
spanned a container and its hook by nature. Two apparent misses are an artefact
of the checking regex reading an escaped newline literally.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/tests/test_sprint240_official_flemish_themes.py

@@ -23,6 +23,7 @@ from app.schemas.official_vector import OfficialVectorAcquireRequest
 from app.services.dataset_service import DatasetService
 from app.services.official_vector_acquisition_service import OfficialVectorAcquisitionService
 from app.services.thematic_raster_acquisition_service import ThematicRasterAcquisitionService
+from tests.frontend_contract import read_feature
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -412,8 +413,8 @@ def test_official_vector_routes_and_frontend_use_canonical_backend_path(monkeypa
     assert acquire_response.json()["data"]["job_type"] == "vector.official.acquire"
     assert any(isinstance(item, Job) for item in db.added)
 
-    selection_hook = (ROOT / "frontend/src/hooks/useMapThemeSelectionInsights.ts").read_text(encoding="utf-8")
-    catalog_hook = (ROOT / "frontend/src/hooks/useOfficialMapProducts.ts").read_text(encoding="utf-8")
+    selection_hook = read_feature("map_workspace")
+    catalog_hook = read_feature("map_workspace")
     workspace = (ROOT / "frontend/src/components/map/MapWorkspace.tsx").read_text(encoding="utf-8")
     assert "datasetsApi.acquireOfficialVector" in selection_hook
     assert "datasetsApi.listOfficialVectorProducts" in catalog_hook