docs: add reference to branch model and human release process in AGENTS.md

Author: kriss145

AGENTS.md

@@ -140,3 +140,4 @@ Releases use [Changesets](https://github.com/changesets/changesets).
 - For any user-facing change, add a changeset: `yarn changeset` (or create a `.changeset/*.md` file with the bump level and summary).
 - **The maintainer runs the release flow** — `yarn prepare-release` (runs `changeset version`, commits the bump, pushes `develop`, creates the `release/vX.Y.Z` branch, and opens the release PR).
 - Agents must **not** run `prepare-release` or `git push` to remote. Prepare locally only — create the changeset and commits — then hand off with the exact command (`yarn prepare-release`). Push/publish only if the maintainer explicitly asks this time.
+- Branch model and the full human release process: see `CONTRIBUTING.md`.