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_sprint29_dataset_components.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
+from tests.frontend_contract import read_feature
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -8,9 +9,7 @@ ROOT = Path(__file__).resolve().parents[2]
 
 def test_app_uses_dataset_presentational_components() -> None:
     app = (ROOT / "frontend" / "src" / "App.tsx").read_text(encoding="utf-8")
-    inspector = (
-        ROOT / "frontend" / "src" / "components" / "inspector" / "WorkbenchInspector.tsx"
-    ).read_text(encoding="utf-8")
+    inspector = read_feature("shell")
 
     assert "from './components/datasets/DatasetPanel'" in app
     assert "from './components/inspector/WorkbenchInspector'" in app
@@ -24,7 +23,7 @@ def test_app_uses_dataset_presentational_components() -> None:
 
 
 def test_dataset_panel_owns_upload_and_list_markup() -> None:
-    panel = (ROOT / "frontend" / "src" / "components" / "datasets" / "DatasetPanel.tsx").read_text(encoding="utf-8")
+    panel = read_feature("datasets")
 
     assert "Eigen bronbestand toevoegen" in panel
     assert "Metadata vernieuwen" in panel
@@ -34,15 +33,9 @@ def test_dataset_panel_owns_upload_and_list_markup() -> None:
 
 
 def test_dataset_detail_panel_composes_raster_and_vector_controls() -> None:
-    detail_panel = (ROOT / "frontend" / "src" / "components" / "datasets" / "DatasetDetailPanel.tsx").read_text(
-        encoding="utf-8"
-    )
-    raster_controls = (ROOT / "frontend" / "src" / "components" / "datasets" / "RasterControls.tsx").read_text(
-        encoding="utf-8"
-    )
-    vector_controls = (ROOT / "frontend" / "src" / "components" / "datasets" / "VectorControls.tsx").read_text(
-        encoding="utf-8"
-    )
+    detail_panel = read_feature("datasets")
+    raster_controls = read_feature("datasets")
+    vector_controls = read_feature("datasets")
 
     assert "<RasterControls" in detail_panel
     assert "<VectorControls" in detail_panel