- GPM channel is system.yaml gpm.releases (testing->stable), not GRAV_CHANNEL
- core upgrade is 'bin/gpm self-upgrade -y'; existing remote-upgrade-grav
target ('bin/grav upgrade') is broken and must be fixed
- add server content-pull + cache-clear + preflight steps to Phase 2
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>