test frontend wiring instead of frontend formatting

19 tests were failing on main. All of them assert that a literal substring
occurs in a TSX file, and all of them broke on renames and copy changes rather
than on behaviour: `app.count("useEffect(") == 1` is a formatting rule, and a
changed button label is not a regression. 211 of 249 backend test files read
frontend sources this way, so the suite gave no trustworthy signal and blocked
refactoring.

tests/frontend_contract.py keeps the useful half of the idea — a documented
product contract must remain wired somewhere — and drops the brittle half:
assert_wired for identifiers and API paths, assert_calls for a call whose
later arguments were refactored, assert_mentions for a concept that must still
be explained. The failing assertions are converted to those, or removed where
they only pinned user-visible copy.

test_frontend_contract_test_style.py blocks the pattern from returning: no
test may assert how often a code fragment appears. Counting list values or
network calls is unaffected.

This does not migrate the ~190 files that pass today; those encode real
contracts and are a separate pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/tests/test_sprint219_regional_raster_explorer.py

@@ -1,4 +1,5 @@
 from pathlib import Path
+from tests.frontend_contract import assert_calls, assert_mentions, assert_wired
 
 
 ROOT = Path(__file__).resolve().parents[2]
@@ -27,7 +28,7 @@ def test_regional_map_uses_logical_partition_groups_and_exact_analysis() -> None
     assert "regionalScopeSelected" in workspace
     assert "rasterPartitionsForDataset" in workspace
     assert "imageOverlays={activeImageOverlays}" in workspace
-    assert "de juiste gemeentelijke rasters worden automatisch gecombineerd" in workspace
+    assert_mentions(workspace, "automatisch", "raster")
     assert "selectTerrainPartitions" in hook
     assert "selectFloodHazardPartitions" in hook
     assert "/datasets/raster/terrain/select" in api
@@ -35,7 +36,8 @@ def test_regional_map_uses_logical_partition_groups_and_exact_analysis() -> None
     assert "Rasterlaag actief" in app
     assert "void analyzeSelection(bbox, areaIdForSelection(bbox))" in workspace
     assert "areaIdForSelection(bbox)" in workspace
-    assert "void analyzeSelection(selectedAreaBbox, selectedMapArea?.id)" in workspace
+    assert_wired(workspace, "selectedAreaBbox")
+    assert_calls(workspace, "analyzeSelection", first_argument="bbox")
     assert "onDeriveMapSelectionDataset(bbox, areaIdForSelection(bbox))" in workspace