ci: add Rollback magi-server Staging workflow

.github/workflows/rollback-staging.yml

@@ -0,0 +1,44 @@
+name: Rollback magi-server Staging
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: "Version to rollback @staging to (e.g. 0.35.2)"
+        required: true
+        type: string
+      reason:
+        description: "Reason for rollback (audit log)"
+        required: true
+        type: string
+
+concurrency:
+  group: npm-publish-magi-server
+  cancel-in-progress: false
+
+jobs:
+  rollback:
+    runs-on: ubuntu-latest
+    environment: npm-publish
+    steps:
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020  # v4.4.0
+        with:
+          node-version: "22"
+          registry-url: "https://registry.npmjs.org"
+
+      - name: Rollback @staging
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+          VERSION: ${{ inputs.version }}
+          REASON: ${{ inputs.reason }}
+        run: |
+          echo "$VERSION" | grep -qE '^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)$' \
+            || { echo "::error::Invalid semver: $VERSION"; exit 1; }
+
+          FOUND=$(npm view "@bash0816/magi-server@${VERSION}" version 2>/dev/null || true)
+          [ "$FOUND" = "$VERSION" ] \
+            || { echo "::error::$VERSION not found on npm registry"; exit 1; }
+
+          echo "ROLLBACK: reason=$REASON target=$VERSION"
+          npm dist-tag add "@bash0816/magi-server@${VERSION}" staging
+          echo "Rolled back @bash0816/magi-server @staging → $VERSION"