chore: add one-shot downstream format fixer

.github/workflows/downstream-format-fix.yml

@@ -0,0 +1,37 @@
+name: Downstream format fix
+
+on:
+  push:
+    branches:
+      - feat/world-packet-boundary-clean-20260929
+
+permissions:
+  contents: write
+
+jobs:
+  format:
+    if: ${{ github.actor != 'github-actions[bot]' }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          ref: feat/world-packet-boundary-clean-20260929
+      - uses: actions/setup-node@v5
+        with:
+          node-version: 24.14.0
+          cache: npm
+      - run: npm ci
+        env:
+          PUPPETEER_SKIP_DOWNLOAD: 1
+      - run: npm run format
+      - name: Commit formatting if needed
+        shell: bash
+        run: |
+          if git diff --quiet; then
+            exit 0
+          fi
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add -A
+          git commit -m "chore: apply adopted formatting"
+          git push