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_sprint201_semantic_selection_metrics.py

@@ -6,6 +6,7 @@ from uuid import uuid4
 from app.models import Dataset
 from app.schemas.operations import VectorSelectionSummary
 from app.services.vector_feature_service import VectorFeatureService
+from tests.frontend_contract import read_feature
 
 
 ROOT = Path(__file__).parents[2]
@@ -174,7 +175,7 @@ def test_regional_historical_polygons_do_not_emit_irrelevant_line_metrics() -> N
 def test_future_regional_imports_persist_semantic_aggregation_configuration() -> None:
     buildings = (ROOT / "scripts/provision_regional_grb_buildings.py").read_text(encoding="utf-8")
     context = (ROOT / "scripts/provision_regional_grb_context.py").read_text(encoding="utf-8")
-    frontend = (ROOT / "frontend/src/components/map/MapWorkspace.tsx").read_text(encoding="utf-8")
+    frontend = read_feature("map_workspace")
 
     assert '"method": "intersection_area"' in buildings
     assert '"label": "Bebouwde grondoppervlakte"' in buildings