Add openapi.json auto-sync workflow

.github/workflows/openapi-sync.yml

@@ -0,0 +1,60 @@
+name: Sync OpenAPI
+
+on:
+  pull_request:
+    paths:
+      - "crates/omnigraph-server/src/**"
+      - "crates/omnigraph-server/Cargo.toml"
+      - "crates/omnigraph-server/tests/openapi.rs"
+
+concurrency:
+  group: openapi-sync-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: write
+
+jobs:
+  sync:
+    name: Regenerate openapi.json
+    # Auto-commit only on same-repo PRs; forks cannot be pushed to.
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@v5.0.1
+        with:
+          ref: ${{ github.head_ref }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y protobuf-compiler libprotobuf-dev
+
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache Rust build data
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: |
+            . -> target
+
+      - name: Regenerate openapi.json
+        run: |
+          OMNIGRAPH_UPDATE_OPENAPI=1 \
+            cargo test --locked -p omnigraph-server --test openapi openapi_spec_is_up_to_date
+
+      - name: Commit if changed
+        run: |
+          if git diff --quiet -- openapi.json; then
+            echo "openapi.json is already in sync."
+            exit 0
+          fi
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add openapi.json
+          git commit -m "chore: regenerate openapi.json"
+          git push