ci: исполнять TS/Python parity на чистом runner (#548)

Issue: #548
User-Visible: no

tests_backend/test_junction_parity.py

@@ -0,0 +1,20 @@
+"""Infrastructure contract of the fail-closed junction parity harness (#548)."""
+from pathlib import Path
+
+import pytest
+
+from junction_parity import DEFAULT_FIXTURE, frontend_rules, load_backend_validator, load_spaces
+
+
+def test_shared_fixture_is_nonempty_and_loads_every_named_scenario():
+    spaces = load_spaces(DEFAULT_FIXTURE)
+    assert len(spaces) == 15
+    assert "angle-14" in spaces
+    assert "distance-5-exact" in spaces
+    assert "debris-node" in spaces
+
+
+def test_missing_typescript_build_is_a_setup_failure_not_a_skip(tmp_path: Path):
+    spaces = load_spaces(DEFAULT_FIXTURE, validator=load_backend_validator())
+    with pytest.raises(FileNotFoundError, match="prerequisites are missing"):
+        frontend_rules(spaces, build_dir=tmp_path / "missing-build")