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/frontend_contract.py

@@ -22,20 +22,77 @@ ROOT = Path(__file__).resolve().parents[2]
 FRONTEND_SRC = ROOT / "frontend" / "src"
 
 
-# The map workspace is one feature split across several modules: the container
-# component, its domain layer and its pure helpers. A contract belongs to the
-# feature, not to whichever file currently holds it, so splitting a 4.000-line
-# component must not red the suite.
-MAP_WORKSPACE_SOURCES = (
-    "components/map/MapWorkspace.tsx",
-    "components/map/mapWorkspaceThemes.ts",
-    "components/map/mapWorkspaceUtils.ts",
-    "hooks/useMapImageOverlays.ts",
-    "hooks/useMapRectangleSelection.ts",
-    "hooks/useFullGisWorkflow.ts",
-    "components/map/MapExplorerView.tsx",
-    "components/map/MapAdvancedWorkbench.tsx",
-)
+# A feature is one behaviour spread over several modules: a container, its
+# hooks, its domain layer, its pure helpers. A contract belongs to the feature,
+# not to whichever file currently holds it, so moving code between siblings
+# must not red the suite. Missing entries are skipped, so a group survives a
+# module being split further, renamed or merged back.
+#
+# Use these for *positive* contracts ("this is wired"). A negative contract
+# ("this component performs no transport") is a statement about one file and
+# must keep reading that file, or widening it would quietly weaken the check.
+FEATURE_SOURCES: dict[str, tuple[str, ...]] = {
+    "map_workspace": (
+        "components/map/MapWorkspace.tsx",
+        "components/map/mapWorkspaceThemes.ts",
+        "components/map/mapWorkspaceUtils.ts",
+        "components/map/MapExplorerView.tsx",
+        "components/map/MapAdvancedWorkbench.tsx",
+        "hooks/useMapImageOverlays.ts",
+        "hooks/useMapRectangleSelection.ts",
+        "hooks/useFullGisWorkflow.ts",
+        "hooks/useMapThemeSelectionInsights.ts",
+        "hooks/useMapSelectionExtract.ts",
+        "hooks/useMapWorkspaceState.ts",
+        "hooks/useMapSelectionDataset.ts",
+        "hooks/useMapSelectionQa.ts",
+        "hooks/useMapThemeSelectionInsights.ts",
+        "hooks/useTemporalComparison.ts",
+        "hooks/useCoverageResolver.ts",
+        "hooks/useOfficialMapProducts.ts",
+    ),
+    "detection": (
+        "components/detection/DetectionLab.tsx",
+        "components/detection/DetectionModelManagement.tsx",
+        "components/detection/detectionProfiles.ts",
+        "components/models/ModelSelector.tsx",
+        "components/models/modelOptions.ts",
+        "hooks/useDetectionWorkflow.ts",
+    ),
+    "segmentation": (
+        "components/segmentation/SegmentationLab.tsx",
+        "hooks/useSegmentationWorkflow.ts",
+    ),
+    "quality": (
+        "components/quality/QualityResultsPanel.tsx",
+        "components/quality/DetectionReviewPanel.tsx",
+        "hooks/useQualityWorkflow.ts",
+    ),
+    "datasets": (
+        "components/datasets/DatasetPanel.tsx",
+        "components/datasets/DatasetDetailPanel.tsx",
+        "components/datasets/RasterControls.tsx",
+        "components/datasets/VectorControls.tsx",
+        "components/datasets/SourceCatalogPanel.tsx",
+        "hooks/useDatasetWorkflow.ts",
+        "services/api/datasets.ts",
+    ),
+    "exports": (
+        "components/exports/ExportCenter.tsx",
+        "hooks/useExportWorkflow.ts",
+    ),
+    "shell": (
+        "App.tsx",
+        "components/shell/WorkbenchNavigation.tsx",
+        "components/shell/SecondaryDisplay.tsx",
+        "components/inspector/WorkbenchInspector.tsx",
+        "components/overview/OverviewWorkspace.tsx",
+        "hooks/useProjectWorkspace.ts",
+        "hooks/useWorkbenchBootstrap.ts",
+    ),
+}
+
+MAP_WORKSPACE_SOURCES = FEATURE_SOURCES["map_workspace"]
 
 
 def read_frontend(relative_path: str) -> str:
@@ -59,10 +116,22 @@ def read_frontend_area(*relative_paths: str) -> str:
     return chr(10).join(parts)
 
 
+def read_feature(name: str) -> str:
+    """Every module of one feature, whichever files it is currently split into."""
+
+    try:
+        sources = FEATURE_SOURCES[name]
+    except KeyError:  # pragma: no cover - a typo should fail loudly
+        raise AssertionError(
+            f"Unknown frontend feature {name!r}; known: {sorted(FEATURE_SOURCES)}"
+        ) from None
+    return read_frontend_area(*sources)
+
+
 def read_map_workspace() -> str:
     """The whole map workspace feature, whichever modules it is split into."""
 
-    return read_frontend_area(*MAP_WORKSPACE_SOURCES)
+    return read_feature("map_workspace")
 
 
 def assert_wired(source: str, *identifiers: str, context: str = "frontend source") -> None: