ci: drop automerge fallback — GitHub Pro enables native auto-merge + branch protection

.github/workflows/automerge-stage.yml

@@ -1,49 +0,0 @@
-# Auto-merge for PRs targeting `stage`.
-#
-# Why this exists: the repo is private on the GitHub Free plan, so native
-# branch protection and native auto-merge are unavailable (both return 403
-# "Upgrade to GitHub Pro"). This workflow is the documented fallback: when a
-# check run completes, it finds open PRs whose head SHA matches and whose base
-# is `stage`, verifies EVERY check is green, and merges. If the repo is ever
-# upgraded (or made public), delete this file and enable native protection +
-# auto-merge on `stage` instead.
-name: Auto-merge to stage
-
-on:
-  check_run:
-    types: [completed]
-
-permissions:
-  contents: write
-  pull-requests: write
-  checks: read
-
-concurrency:
-  group: automerge-stage-${{ github.event.check_run.head_sha }}
-  cancel-in-progress: false
-
-jobs:
-  merge:
-    runs-on: ubuntu-latest
-    timeout-minutes: 5
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Merge green stage PRs for this head SHA
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          HEAD_SHA: ${{ github.event.check_run.head_sha }}
-        run: |
-          set -euo pipefail
-          prs=$(gh pr list --state open --base stage --limit 50 --json number,headRefOid \
-            --jq ".[] | select(.headRefOid == \"$HEAD_SHA\") | .number")
-          for pr in $prs; do
-            echo "Checking PR #$pr ($HEAD_SHA)"
-            # Fail (skip) if any check is not green.
-            if gh pr checks "$pr" --json name,state --jq '.[] | select(.state != "SUCCESS")' | grep -q .; then
-              echo "PR #$pr still has pending/failing checks — not merging."
-              continue
-            fi
-            gh pr merge "$pr" --merge --delete-branch=false
-            echo "Merged PR #$pr into stage."
-          done