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_sprint197_accuracy_review_loop.py

@@ -19,6 +19,7 @@ from app.schemas.detection_review import (
     DetectionReviewUpsert,
 )
 from app.services.detection_review_service import DetectionReviewService
+from tests.frontend_contract import read_feature
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -241,7 +242,7 @@ def test_detection_review_endpoints_use_canonical_envelopes(monkeypatch) -> None
 
 def test_map_detection_qa_uses_documented_footprint_threshold_and_honest_labels() -> None:
     hook = (ROOT / "frontend" / "src" / "hooks" / "useMapOrthophotoAnalysis.ts").read_text(encoding="utf-8")
-    app_source = (ROOT / "frontend" / "src" / "App.tsx").read_text(encoding="utf-8")
+    app_source = read_feature("shell")
     evidence_service = (ROOT / "backend" / "app" / "services" / "quality_evidence_service.py").read_text(encoding="utf-8")
 
     assert "MAP_BUILDING_QA_IOU_THRESHOLD = 0.25" in hook