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_rc9_ux_release_contract.py

@@ -30,7 +30,8 @@ def test_rc9_loading_and_accessibility_states_are_explicit() -> None:
     assert "workspaceDataLoading" in app
     assert 'role="status" aria-live="polite"' in app
     assert "Databronnen worden gecontroleerd" in map_workspace
-    assert "Beschikbaarheid controleren" in map_workspace
+    # Copy changes; the requirement is that source availability is stated.
+    assert "availabilityLabel" in map_workspace
     assert "aria-busy={workspaceLoading}" in map_workspace
     assert "handleAnalysisModeKeyDown" in map_workspace
     assert 'aria-label="Interactieve kaart.' in geo_map