Extracts the land half of /land-and-deploy into a standalone, composable
skill: pre-flight, CI wait, VERSION-drift, the pre-merge readiness gate
(with --fast), and a regime-aware merge that drives bin/gstack-merge.
Confirms landing (state==MERGED + commit on base, handling rebase-null oid)
and writes the last-land.json handoff. Carries the never-blind-retry
post-failure invariant (cli/cli#3442, cli/cli#13380).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Garry Tan