_startup_login() ran garminconnect's login synchronously with no timeout
before main() ever started reading stdin, so a slow/rate-limited Garmin
login could wedge a user's whole subprocess before it became responsive.
Give it the same background-thread + bounded-10s-timeout shape
_handle_authenticate already uses, with tests for both the fast-success
and timeout paths.
Also refreshes .claude/skills/geniusrun-dev/SKILL.md (still describing
the retired mcp-garmin MCP architecture) and three stale doc comments
(garmin.AuthStatus, config.GarminTokenStoreRoot, mock package doc) left
over from the direct-wrapper migration.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>