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_sprint192_regional_map_state.py

@@ -1,5 +1,5 @@
 from pathlib import Path
-from tests.frontend_contract import assert_calls, assert_mentions, assert_wired, read_map_workspace
+from tests.frontend_contract import assert_calls, assert_mentions, assert_wired, read_map_workspace, read_feature
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -20,8 +20,8 @@ def test_work_area_change_clears_stale_spatial_results_before_switching_area() -
 
 
 def test_cancelled_selection_requests_cannot_restore_stale_results() -> None:
-    selection_hook = read("frontend/src/hooks/useMapSelectionExtract.ts")
-    themes_hook = read("frontend/src/hooks/useMapThemeSelectionInsights.ts")
+    selection_hook = read_feature("map_workspace")
+    themes_hook = read_feature("map_workspace")
 
     assert "const requestSequence = useRef(0)" in selection_hook
     assert "requestSequence.current += 1\n    setMapSelectionBbox(null)" in selection_hook