v2.3.1 — Windows MCP hang hotfix (#46, #136)

Summary

Hotfix for the Windows long-running MCP tool hang. v2.2.4 shipped the event-loop policy fix, but @dev-limucc's test on #136 showed that was necessary but not sufficient — read-only tools worked, but build_or_update_graph_tool and embed_graph_tool still hung indefinitely on Windows 11 / Python 3.14.

uvx --reinstall code-review-graph
# or
pip install -U code-review-graph

If you were affected by either #46 or #136 on v2.2.4, this release should fix it.

What's fixed

FastMCP 2.x dispatches sync handlers inline on the only event-loop thread. When a handler runs for more than a few seconds — especially one that spawns subprocesses (full_build uses ProcessPoolExecutor) or does CPU-bound inference (sentence-transformers) — the loop stops pumping stdin/stdout, Claude Code's request never gets a response, and the MCP client shows "Synthesizing…" forever.

Fix: the five heavy tools are now async def and offload their blocking work with asyncio.to_thread. The event loop stays responsive and stdio keeps pumping.

Tools now async

• build_or_update_graph_tool — full_build / incremental_update
• run_postprocess_tool — community detection can take 20s+ on large graphs
• embed_graph_tool — sentence-transformers / Gemini inference
• detect_changes_tool — git diff subprocess + BFS traversal
• generate_wiki_tool — many SQLite reads + file writes

The other 19 tools are fast SQLite-read paths and stay sync.

Lock-in tests

Two new regression tests in tests/test_main.py::TestLongRunningToolsAreAsync:

1. test_heavy_tools_are_coroutines — asserts via mcp.get_tools() introspection that all 5 heavy tools register as coroutine functions.
2. test_heavy_tool_source_uses_to_thread — greps each tool's source for a literal asyncio.to_thread call, so we don't accidentally make a tool async def without actually offloading the work.

These will fail at collection time if someone converts one of the 5 tools back to sync in a future refactor.

Verification

macOS / Python 3.11:

• All 24 tools register, 5 heavy ones as coroutines
• 737 tests pass (+2 new lock-in tests), coverage 74.63%
• ruff / mypy / bandit clean
• CI matrix 3.10 / 3.11 / 3.12 / 3.13 green

Windows: will be verified by @dev-limucc post-release against the original repro (build_or_update_graph_tool(full_rebuild=True) + embed_graph_tool).

Upgrade notes

• Nothing to do beyond upgrading. The async wrappers are transparent to MCP clients — they still call the tools the same way.
• If you're coming from v2.2.2 or earlier, the usual code-review-graph install is still needed to pick up the v2.2.3 hook schema rewrite.

Closes (pending final Windows test)

• #46 (build hangs on Windows)
• #136 (embed_graph_tool hangs on Windows)