Add timeout to _run_sync to prevent indefinite blocking

Use the connection timeout for future.result() so the calling thread
doesn't block forever if the server hangs or the event loop dies.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitedbapi/connection.py

@@ -58,7 +58,11 @@ def _run_sync(self, coro: Any) -> Any:
         """
         loop = self._ensure_loop()
         future = asyncio.run_coroutine_threadsafe(coro, loop)
-        return future.result()
+        try:
+            return future.result(timeout=self._timeout)
+        except TimeoutError as e:
+            future.cancel()
+            raise OperationalError(f"Operation timed out after {self._timeout} seconds") from e
 
     async def _get_async_connection(self) -> DqliteConnection:
         """Get or create the underlying async connection."""

tests/test_run_sync_timeout.py

@@ -0,0 +1,20 @@
+"""Tests for _run_sync timeout behavior."""
+
+import asyncio
+
+import pytest
+
+from dqlitedbapi.connection import Connection
+from dqlitedbapi.exceptions import OperationalError
+
+
+class TestRunSyncTimeout:
+    def test_run_sync_times_out(self) -> None:
+        """_run_sync should raise OperationalError after timeout."""
+        conn = Connection("localhost:9001", timeout=0.1)
+
+        async def hang_forever() -> None:
+            await asyncio.sleep(999)
+
+        with pytest.raises(OperationalError, match="timed out"):
+            conn._run_sync(hang_forever())