Two fixes for multi-runtime installations:
1. Update cache now writes to ~/.cache/gsd/ instead of the runtime-
specific config dir, preventing mismatches when check-update and
statusline resolve to different runtimes. Statusline reads from
shared path first with legacy fallback.
2. Stale hooks detection now checks configDir/hooks/ where hooks are
actually installed, not configDir/get-shit-done/hooks/ which does
not exist.
Closes#1421
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>