docs: add human approval gate to release process (#73)

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

Author: zvikagart

RELEASE.md

@@ -5,7 +5,14 @@
     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.
+
+    > **⚠️ Automated agents: stop after step 1.** Open the release PR, then hand
+    > control back to the user. A human performs this step. 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 to the steps below after the
+    > user explicitly tells you to proceed.
 1. Locally, sync your clone with GitHub:
     ```
     git fetch origin
@@ -21,5 +28,4 @@
     git push origin vX.Y.Z
     ```
 
-    This will trigger a workflow on CircleCI that will generate a GitHub release
-    and publish the new version to PyPI.
+    This will trigger a workflow on CircleCI that will publish the new version to PyPI.