chore(deps): bump libtmux floor to 0.55.1

[tony]

Summary

Bump the runtime floor of libtmux from >=0.55.0 to >=0.55.1 and refresh uv.lock to install 0.55.1.

libtmux 0.55.1 ships the pytest-plugin socket-reaper fix (tmux-python/libtmux#661): the server and TestServer fixtures now kill the tmux daemon AND unlink the socket file under /tmp/tmux-<uid>/ on teardown. That's the upstream root-cause fix for the test-socket leak reported in #20.

Effect on open PRs

Supersedes #23 (local conftest reaper). The local reaper was a downstream workaround for the same issue #661 fixes upstream. Once this bump lands, PR #23's fixture adds no behavior beyond what libtmux already does on teardown — it becomes pure churn. Recommend closing #23 without merge.

Unaffected: #21 (async channel waits), #22 (is_caller socket scope). Both are libtmux-mcp-only bugs with no upstream analog.

Test plan

• uv run ruff check . --fix --show-fixes
• uv run ruff format .
• uv run mypy
• uv run py.test --reruns 0 -vvv (363 passed)
• just build-docs

End-to-end verification: after the bump, a clean uv run pytest from an empty /tmp/tmux-<uid>/libtmux_test* state leaves 1 residual socket (down from thousands accumulating across runs pre-fix). The lone straggler originates outside the standard fixture teardown path — a separate, minor issue, tracked separately if it matters.

Companion PRs

• fix(wait_for_tools): unblock event loop via asyncio.to_thread #21 — event-loop block in channel waits (closes wait_for_channel and signal_channel block the FastMCP event loop (sync subprocess.run) #18, unaffected)
• fix(_utils): scope is_caller annotation to caller's socket #22 — is_caller socket-blind false positive (closes is_caller annotation gives false positives across tmux sockets #19, unaffected)
• test(conftest): reap leaked libtmux_test* sockets after session #23 — local reaper (closes list_servers exposes dozens of leaked libtmux_test* tmux daemons after test runs #20) — superseded by this PR, close without merge
• Upstream: tmux-python/libtmux#661 — shipped in libtmux 0.55.1

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.78%. Comparing base (58af71f) to head (2a7b18d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #24      +/-   ##
==========================================
- Coverage   87.01%   86.78%   -0.24%     
==========================================
  Files          38       38              
  Lines        1710     1710              
  Branches      201      201              
==========================================
- Hits         1488     1484       -4     
- Misses        164      167       +3     
- Partials       58       59       +1     

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