chore(agents): document Renovate platform auto-merge prerequisites

Captures the lesson from wiring up auto-merge: a restrictive Renovate
`schedule` gates Renovate's own merge step, so platform (GitHub-native)
auto-merge is needed to merge green PRs outside the window, which in turn
needs the repo "Allow auto-merge" setting plus branch protection with the
CI checks required (non-strict, admins exempt).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ChipWolf

home/dot_agents/AGENTS.md

@@ -62,6 +62,7 @@ Always edit the source, not the deployed file. When updating any memory file: re
 - **Inspecting a PR's diff.** Always diff the remote PR branch against `origin/main` (e.g. `git diff origin/main...origin/<pr-branch>`), not local HEAD. Local HEAD may be on an unrelated branch, so a diff against it is meaningless and returns empty output without any error.
 - **Before opening a PR: clean up history.** Squash messy work-in-progress or AI-attributed commits into a clean, atomic commit sequence on the branch. The branch is yours until `gh pr create` succeeds.
 - **Once a PR is open: never amend or force-push.** Use follow-up commits so reviewers see exactly what changed between their review and your response. The branch now belongs to the reviewer; rewriting it erases the diff they expect to see. Preserve every change as a separate commit.
+- **Renovate auto-merge needs platform prerequisites, not just `automerge: true`.** With a restrictive top-level `schedule`, Renovate's own merge step only runs inside that window, so green PRs can sit unmerged for days. To merge whenever checks pass, rely on GitHub-native auto-merge (`platformAutomerge`, default true): it requires the repo's "Allow auto-merge" setting enabled AND branch protection on the target branch with the CI checks marked required. Set those required checks non-strict (do not require the branch be up to date) so a rebase schedule cannot deadlock merges, and leave admins exempt so the owner's direct pushes still work. Diagnose "automerge configured but PRs piling up" by correlating the last successful auto-merge against recent `schedule`/config commits, then verify the fix non-destructively by enabling auto-merge on a failing PR: GitHub should accept it but hold it (BLOCKED), not merge.
 
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