docs: explain BEGIN_COMMIT_OVERRIDE for PRs with several changes (#2445)

A squash merge keeps only the PR title, so release-please lists one
changelog entry per PR. Document the commit override block for PRs that
contain several changes that should be listed separately.

Author: kikoso

AGENTS.md

@@ -73,6 +73,21 @@ into the root `settings.gradle.kts`; build them from their own directory.
   prefix causes a wrong release bump.
 - **PR Title Validation**: Ensure PR titles strictly conform to Conventional Commits (e.g., `fix: stale QuadItem removal` instead of `Fix stale QuadItem removal`). When PRs are squash-merged into `main`, GitHub uses the PR title as the default commit header; a non-conforming title prevents release-please from accurately categorizing changes in CHANGELOG.md or calculating semantic version increments.
 - Never edit CHANGELOG.md or `.release-please-manifest.json` by hand.
+- **Several changes in one PR**: a squash merge keeps only the PR title, so
+  release-please would list one entry. When a PR contains several changes that
+  belong in the changelog separately (for example several bug fixes), add a
+  commit override block at the end of the PR description, one Conventional
+  Commit per line. release-please uses these lines instead of the PR title:
+
+  ```
+  BEGIN_COMMIT_OVERRIDE
+  fix(ApiDemos): describe the first fix
+  fix(snippets): describe the second fix
+  END_COMMIT_OVERRIDE
+  ```
+
+  The PR title still has to be a valid Conventional Commit. Each line counts
+  for the version bump, so a `feat:` or `!` line bumps accordingly.
 - All pull requests are to be created as drafts (`gh pr create --draft`) until authorization is explicitly given to mark them ready for review. Always inform the user that the PR was created as a draft.
 - Keep changes scoped to one sample or one feature across its language
   variants; do not mix unrelated samples in one PR.