Fixed the actual root cause instead of just masking it in tests:
1. Root Problem:
- C++ side's ZmqDistanceComputer creates ZMQ connections but doesn't clean them
- Python 3.9/3.13 are more sensitive to cleanup timing during shutdown
2. Core Fixes in SearcherBase and LeannSearcher:
- Added cleanup() method to BaseSearcher that cleans ZMQ and embedding server
- LeannSearcher.cleanup() now also handles ZMQ context cleanup
- Both HNSW and DiskANN searchers now properly delete C++ index objects
3. Backend-Specific Cleanup:
- HNSWSearcher.cleanup(): Deletes self.index to trigger C++ destructors
- DiskannSearcher.cleanup(): Deletes self._index and resets state
- Both force garbage collection after deletion
4. Test Infrastructure:
- Added auto_cleanup_searcher fixture for explicit resource management
- Global cleanup now more aggressive with ZMQ context destruction
This is the proper fix - cleaning up resources at the source, not just
working around the issue in tests. The hanging was caused by C++ side
ZMQ connections not being properly terminated when is_recompute=True.
a6dad47280