fix: preserve legacy plugin catalogs and protect helper token initialization

tests/unit/runtime/test_helper_manager.py

@@ -214,6 +214,54 @@ def test_concurrent_managers_share_the_first_host_token(tmp_path, monkeypatch):
     assert token_path.read_text() == tokens[0]
 
 
+def test_unreadable_host_token_is_not_replaced(tmp_path, monkeypatch):
+    monkeypatch.setattr(hm, "get_temp_dir", lambda _name: tmp_path / "mutex")
+    token_path = tmp_path / "session.token"
+    token_path.write_text("a" * 48)
+    original_read = Path.read_text
+
+    def denied(path, *args, **kwargs):
+        if path == token_path:
+            raise PermissionError("token temporarily inaccessible")
+        return original_read(path, *args, **kwargs)
+
+    monkeypatch.setattr(Path, "read_text", denied)
+    manager = AccessibilityHelperManager(token_path=token_path)
+    with pytest.raises(PermissionError, match="temporarily inaccessible"):
+        manager.host_token()
+    assert original_read(token_path) == "a" * 48
+    monkeypatch.setattr(Path, "read_text", original_read)
+    assert manager.host_token() == "a" * 48
+
+
+def test_live_provision_mutex_cannot_be_stolen_after_lease_ages(tmp_path, monkeypatch):
+    import hashlib
+    import os
+    import threading
+    import time
+
+    monkeypatch.setattr(hm, "get_temp_dir", lambda _name: tmp_path)
+    first = AccessibilityHelperManager()
+    second = AccessibilityHelperManager()
+    entered = threading.Event()
+
+    def contender():
+        with second._provision_mutex(SERIAL):
+            entered.set()
+
+    with ThreadPoolExecutor(max_workers=1) as executor:
+        with first._provision_mutex(SERIAL):
+            digest = hashlib.sha256(SERIAL.encode()).hexdigest()[:16]
+            path = tmp_path / f"{digest}.mutex"
+            old = time.time() - hm._PROVISION_MUTEX_STALE_SECONDS - 10
+            os.utime(path, (old, old))
+            future = executor.submit(contender)
+            stolen = entered.wait(0.2)
+        future.result(timeout=5)
+    assert not stolen
+    assert entered.is_set()
+
+
 # --------------------------------------------------------------------------- #
 # Provision
 # --------------------------------------------------------------------------- #