fix(ci): set GH_REPO in release-please auto-merge step

The auto-merge step runs in a job with no actions/checkout, so gh could not
infer the repository from a git remote and failed with 'not a git repository'
(#719 follow-up). Set GH_REPO=${{ github.repository }} so gh pr list/review/
merge work without a checkout — same fix as the whatsnew workflow (2a5f0a8).

Confirmed working otherwise: with RELEASE_PLEASE_TOKEN set, release PR #721 is
now PAT-authored and its required checks run automatically (no manual approval).

.github/workflows/release-please-beta.yml

@@ -41,6 +41,9 @@ jobs:
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           RELEASE_PAT: ${{ secrets.RELEASE_PLEASE_TOKEN }}
+          # This job has no checkout, so gh can't infer the repo from a git
+          # remote — set it explicitly (same pattern as whatsnew, 2a5f0a8).
+          GH_REPO: ${{ github.repository }}
         run: |
           if [ -z "$RELEASE_PAT" ]; then
             echo "RELEASE_PLEASE_TOKEN not set — skipping auto-merge (manual review still required)."

.github/workflows/release-please.yml

@@ -34,6 +34,9 @@ jobs:
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           RELEASE_PAT: ${{ secrets.RELEASE_PLEASE_TOKEN }}
+          # No checkout in this job — set the repo explicitly so gh works
+          # without a git remote (same pattern as whatsnew, 2a5f0a8).
+          GH_REPO: ${{ github.repository }}
         run: |
           if [ -z "$RELEASE_PAT" ]; then
             echo "RELEASE_PLEASE_TOKEN not set — skipping auto-merge (manual review still required)."