docs: add human approval gate to release process

Make explicit that automated agents must stop after opening the release
PR and wait for a human to review, approve, and merge it. Note that
pushing the release tag publishes to PyPI and is irreversible.

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

Author: zvikagart

RELEASE.md

@@ -1,11 +1,18 @@
 # Version Release Process
 
+> **⚠️ Automated agents: stop after step 1.** Open the release PR, then hand
+> control back to the user. A human must review, approve, and merge the PR
+> (step 2). Do **not** merge the PR, create the tag, or push the tag on your
+> own — pushing the tag publishes to PyPI and **cannot be undone**. Only
+> continue past step 1 after the user explicitly tells you to proceed.
+
 1. Open a PR with the following changes:
     1. Bump the version in [pyproject.toml](pyproject.toml).
     1. Update the [CHANGELOG.md](CHANGELOG.md).
     1. If the change requires a newer Code Ocean server version, update `MIN_SERVER_VERSION` in [client.py](src/codeocean/client.py).
     1. Commit the updates with the message `Bump version to X.Y.Z`.
-1. Merge the PR.
+1. **Review, approve, and merge the PR.** This is a manual step performed by a
+   human after CI passes — it is the approval gate for the release.
 1. Locally, sync your clone with GitHub:
     ```
     git fetch origin