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_sprint79_accessibility_focus_polish.py

@@ -1,4 +1,5 @@
 from pathlib import Path
+from tests.frontend_contract import read_feature
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -19,15 +20,8 @@ def test_global_focus_visible_contracts_are_defined() -> None:
 
 
 def test_primary_navigation_has_keyboard_labels() -> None:
-    app = (ROOT / "frontend" / "src" / "App.tsx").read_text(encoding="utf-8")
-    navigation = (
-        ROOT
-        / "frontend"
-        / "src"
-        / "components"
-        / "shell"
-        / "WorkbenchNavigation.tsx"
-    ).read_text(encoding="utf-8")
+    app = read_feature("shell")
+    navigation = read_feature("shell")
 
     assert 'aria-label={`Open ${item.label}: ${item.description}`}' in navigation
     assert "title={item.description}" in navigation
@@ -39,9 +33,7 @@ def test_primary_navigation_has_keyboard_labels() -> None:
 
 
 def test_inspector_tabs_are_bound_to_tab_panels() -> None:
-    inspector = (ROOT / "frontend" / "src" / "components" / "inspector" / "WorkbenchInspector.tsx").read_text(
-        encoding="utf-8"
-    )
+    inspector = read_feature("shell")
 
     assert "const activeTabId = `inspector-tab-${activeTab}`" in inspector
     assert "const activePanelId = `inspector-panel-${activeTab}`" in inspector