fix(gaia-wiki): wait for merge and clean up locally when finishing the chain

[stevensacks]

Problem

/gaia-wiki's finish (gaia wiki chain finish, and sync land's protected-branch path) fired gh pr merge --squash --auto --delete-branch then immediately git checkout main and returned. --auto only queues the merge, so the CLI never waited for it: local main was never pulled to reflect the merged content, and the local wiki-sync/* branch was never deleted. The remote branch got auto-deleted on merge later, but the local one lingered until the session-start janitor eventually swept it.

Fix

Finish now lands like any other PR, following the "safe pattern" in wiki/concepts/PR Merge Workflow.md:

1. Enable auto-merge (--auto waits for the gate to go green server-side).
2. Poll gh pr view <branch> --json state until MERGED.
3. Clean up locally: git checkout main → git pull --ff-only origin main → git branch -D <branch> → git fetch --prune origin.
4. Graceful degradation: if the merge doesn't land within the bounded wait, auto-merge stays queued (GitHub completes it once checks pass) and local cleanup is deferred to the session-start janitor — the CLI never hard-fails here.

The chain determinism contract forbids the router from inlining git/gh, so the wait+cleanup lives in a shared finalizeMerge helper in .gaia/cli/src/wiki/util/land.ts. Both chain finish and sync land's protected-branch landing route through it (the latter had the identical non-waiting bug), removing the duplicated finish tail.

Notes

• Diff is entirely under .gaia/ + .claude/ + root markdown, so it's out of code-review-audit scope — the merge gate's out-of-scope bypass clears it with no marker.
• Bundled binaries (.gaia/cli/gaia, gaia-maintainer) rebuilt.
• Poll budget defaults to 10 × 30s; wiki-only PRs typically have no required checks so it returns on the first poll.

Testing

• .gaia/cli typecheck clean; full CLI suite 1477 passed / 1 skipped.
• Added merged-path and timeout-path tests for both chain finish and sync land.

🤖 Generated with Claude Code

[github-actions]

code-review-audit skipped: no audit-relevant files changed in the un-audited delta (since the last clean audit); GAIA-Audit commit status stamped on HEAD so the merge gate is satisfied with no local audit run

[github-actions]

code-review-audit skipped: no audit-relevant files changed in the un-audited delta (since the last clean audit); GAIA-Audit commit status stamped on HEAD so the merge gate is satisfied with no local audit run