Stabilize context-overflow compaction test in Python 3.11 CI (#1006)

* Stabilize overflow compaction test expectations

Co-authored-by: eous <13773563+eous@users.noreply.github.com>

* Fix ObservedRLock compatibility with Python 3.14 Condition

Co-authored-by: eous <13773563+eous@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eous <13773563+eous@users.noreply.github.com>

tests/test_cancel.py

@@ -225,6 +225,9 @@ class _ObservedRLock:
     def release(self) -> None:
         self._lock.release()
 
+    def locked(self) -> bool:
+        return self._lock.locked()
+
     def __enter__(self):
         self.acquire()
         return self

tests/test_tool_truncation.py

@@ -225,6 +225,7 @@ class TestContextOverflowRecovery:
             patch.object(session, "_stream_response", side_effect=mock_stream_response),
             patch.object(session, "_compact_messages", compact_mock),
             patch.object(session, "_full_messages", return_value=[]),
+            patch.object(session, "_over_soft", return_value=False),
             patch.object(session, "_update_token_table"),
             patch.object(session, "_print_status_line"),
             patch.object(session, "_emit_state"),