fix(ci): enable release-PR auto-merge with the PAT, not GITHUB_TOKEN

Auto-merge enabled via GITHUB_TOKEN attributes the eventual merge commit to
github-actions[bot], so recursion prevention suppresses the resulting push to
main — the follow-up release-please run that cuts the tag/release never fires.
Net: the version PR merges but no release/tag/images are ever produced (#719).

Enable auto-merge with RELEASE_PLEASE_TOKEN instead (a real identity) so the
merge triggers the tag-cutting run. Approval stays on GITHUB_TOKEN because it
must be a different identity than the PR author (the PAT) to count as a review.

Observed on #723: merged 3.77.3-beta.0 but no run followed and no tag was cut.

.github/workflows/release-please.yml

@@ -44,8 +44,11 @@ jobs:
           fi
           pr=$(gh pr list --head release-please--branches--stable --state open --json number --jq '.[0].number // empty')
           if [ -n "$pr" ]; then
+            # Approve as github-actions[bot] (GITHUB_TOKEN, ≠ the PAT author) so it
+            # is a valid review; enable auto-merge as the PAT so the merge commit is
+            # attributed to a real identity and triggers the tag-cutting run (#719).
             gh pr review "$pr" --approve --body "Automated approval — release-please version bump + changelog (#719)." || true
-            gh pr merge "$pr" --squash --auto || true
+            GH_TOKEN="$RELEASE_PAT" gh pr merge "$pr" --squash --auto || true
           else
             echo "No open release PR to auto-merge."
           fi