v0.7.7 — version metadata fix

v0.7.7 — version metadata fix

Hotfix for v0.7.6: that wheel's metadata said 0.7.6 while
mcptoon --version printed 0.7.5 — the hardcoded __version__ in
src/mcptoon/__init__.py was missed by the release bump. Caught by the
post-release smoke test (fresh venv, official PyPI index), which is now
part of the written release checklist.

• __version__, pyproject.toml and server.json all say 0.7.7.
• tests/test_registry_sync.py pins mcptoon.__version__ against
  pyproject, so the next bump updates all of them or fails CI.

No other changes. See v0.7.6 for the 2026-07-28 GA server bridge and the
official Claude Code plugin.