docs: tell contributors to enable auto-merge

AGENTS.md

@@ -17,3 +17,14 @@ Example:
 | `target` | `es2025` | Emitted language version  |
 
 After creating or updating a file that contains prose, including Markdown files, do reading passes over it until every rule above is satisfied. Fix any violation you find, then read the file again.
+
+## Pull requests
+
+Turn on auto-merge for every pull request you open, so it merges as soon as it is approved and the checks pass.
+
+1. Open the pull request with `gh pr create`.
+2. Run `gh pr merge <number> --auto --merge` on it. A merge commit is the only merge method the repository allows.
+
+- A draft cannot have auto-merge. Mark it ready with `gh pr ready <number>` first, then run the command above.
+- When the user asks to keep a pull request open, leave auto-merge off. If it is already on, turn it off with `gh pr merge <number> --disable-auto`.
+- Release pull requests (`chore: release X.Y.Z`) get auto-merge too. The release starts only when the maintainer pushes the `vX.Y.Z` tag on the merge commit by hand, as `CONTRIBUTING.md` describes.

CONTRIBUTING.md

@@ -133,6 +133,9 @@ Write the description in the imperative mood, such as "add scope rule". Mark a b
 - Link the issue it addresses.
 - Update the changelog and README in the same pull request.
 - Use a title that follows the commit convention.
+- If you have write access, turn on auto-merge once the pull request is open, with `gh pr merge <number> --auto --merge` or the "Enable auto-merge" button. It then merges as soon as it is approved and the checks pass.
+- If auto-merge is off, the author merges the pull request once it is approved and the checks pass. A maintainer merges pull requests opened by a bot or by a contributor without write access.
+- Update the branch when it falls behind `main`, because auto-merge waits until the branch is up to date. The update dismisses the approval, so the pull request needs a new review.
 
 ## License