feat(runtime): enforce governed mutation boundaries

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a06ba0-10aa-7ea0-b20a-4f3fac39efe9

tests/test_runner.py

@@ -8,6 +8,7 @@ import pytest
 import yaml
 
 from rein_aharness.manifest import HARNESS_MAJOR
+from rein_aharness.repository_transaction import RepositoryTransaction
 from rein_aharness.runner import RunResult, run_task
 from rein_aharness.taskspec import TaskSpec, TaskSpecError
 
@@ -148,6 +149,26 @@ def test_run_task_records_bounded_cancellation_without_session_output(tmp_path)
     assert result.reason == "execution cancelled (lease-loss)"
 
 
+def test_run_task_timeout_releases_repository_lock(tmp_path) -> None:
+    repo = _make_repo(tmp_path)
+
+    class TimingOutAdapter:
+        def execute_prompt(self, prompt, config):
+            raise TimeoutError("adapter deadline elapsed")
+
+    result = run_task(
+        _spec(repo),
+        adapter=TimingOutAdapter(),
+        report_to_hub=False,
+        write_metrics=False,
+    )
+
+    assert result.ok is False
+    assert result.reason == "session failed: adapter deadline elapsed"
+    with RepositoryTransaction(repo) as retry:
+        assert retry.locked is True
+
+
 def test_run_task_refuses_unknown_tool_profile(tmp_path) -> None:
     repo = _make_repo(tmp_path)
     _write_manifest(