merge-ready.sh: hardcoded --merge silently dead-locks consumer repos with merge-method rulesets; gh errors are swallowed #201

Summary

merge-ready.sh hardcodes gh pr merge --merge and discards gh's stderr. In any consumer repo whose branch ruleset restricts allowed merge methods, every bot merge is rejected by GitHub and the script logs only a bare {"action":"merge-failed"} — indistinguishable from a transient failure, forever, on every tick.

Incident (reDeploy, 2026-07-24 → 2026-07-30)

• reDeploy's "Main Branch Protection" ruleset allows squash only (created 2026-06-11, dormant while the repo was private on the free plan — rulesets don't enforce there).
• The repo went public on 2026-07-23, activating the ruleset.
• From the next owner approval onward, the bot's --merge was rejected: 435 consecutive silent merge-failed ticks. PR feat(core): first-class upgradeable contracts (UUPS/Transparent proxies) — #155 reDeploy#169 sat green + owner-approved for 5 days and was re-approved 3× to no effect; PRs loop-census.sh: advance_ready eligibility ignores needs-human label, only matches feat/issue-N-* branches #170/fix(needs-human): REST label ops + confirmed-episode guard — stop per-tick comment spam (issue #169) #171 then queued the same way.
• Owner merges by hand kept working (RepositoryRole admin bypass), which masked the breakage.
• Diagnosis required reproducing the exact command outside the daemon because the script swallows the error (>/dev/null 2>&1).
• Interim fix applied repo-side: reDeploy's ruleset now also allows merge. The script defect remains latent for every other consumer.

Proposed fixes

1. Don't hardcode the merge method. Read it from the adapter (gates.json → e.g. merge.method) and/or fall back to what the repo actually permits (gh api repos/{repo}/rulesets → pull_request.parameters.allowed_merge_methods, and the repo's allow_*_merge flags). A squash-only repo should get --squash automatically.
2. Surface the error. Capture gh pr merge stderr and include it in the merge-failed JSON line ("error": "..."), so one journal read identifies the cause instead of requiring an out-of-band repro.
3. Distinguish remote-merge failure from local cleanup failure. With --delete-branch, gh exits non-zero if the head branch is checked out in a .claude/worktrees/ worktree even though the remote merge succeeded. The script then reports merge-failed on a merged PR and skips clean_worktree, leaving exactly the debris that census can mistake for in-flight work. Check the PR's merged state (or split the merge and the branch deletion) before deciding what to report.

Notes

• reCode itself doesn't trip on this today only because its own ruleset has no pull_request rule — the defect is in the shipped script, so every consumer repo with a merge-method restriction inherits it.
• Observed on the merge-ready.sh generation that runs all gh calls via bot-gh.sh (two-root derivation, scripts break when run from the plugin install cache (CLAUDE_PLUGIN_ROOT): root derived as ../.. conflates plugin root with consumer project root #63) as well as reDeploy's older vendored copy.