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_sprint194_regional_timeseries.py

@@ -16,6 +16,7 @@ from rasterio.transform import from_origin
 
 from app.models import Dataset
 from app.services.vector_feature_service import VectorFeatureService
+from tests.frontend_contract import read_feature
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -240,11 +241,11 @@ def test_regional_timeseries_operator_is_packaged_and_release_checked() -> None:
 
 def test_end_user_dataset_sources_are_human_readable() -> None:
     display = (ROOT / "frontend/src/lib/datasetDisplay.ts").read_text(encoding="utf-8")
-    workspace = (ROOT / "frontend/src/components/map/MapWorkspace.tsx").read_text(encoding="utf-8")
-    catalog = (ROOT / "frontend/src/components/datasets/DatasetPanel.tsx").read_text(encoding="utf-8")
+    workspace = read_feature("map_workspace")
+    catalog = read_feature("datasets")
     status = (ROOT / "frontend/src/components/WorkbenchStatusStrip.tsx").read_text(encoding="utf-8")
-    detection = (ROOT / "frontend/src/components/detection/DetectionLab.tsx").read_text(encoding="utf-8")
-    exports = (ROOT / "frontend/src/components/exports/ExportCenter.tsx").read_text(encoding="utf-8")
+    detection = read_feature("detection")
+    exports = read_feature("exports")
 
     assert "department_omgeving_land_use: 'Departement Omgeving'" in display
     assert "statbel: 'Statbel'" in display