feat(ci): add breaking change detection workflow

Author: stainless-app[bot]

.github/workflows/detect-breaking-changes.yml

@@ -6,6 +6,34 @@ on:
       - next
 
 jobs:
+  detect_breaking_changes:
+    runs-on: 'ubuntu-latest'
+    name: detect-breaking-changes
+    if: github.repository == 'openai/openai-node'
+    steps:
+      - name: Calculate fetch-depth
+        run: |
+          echo "FETCH_DEPTH=$(expr ${{ github.event.pull_request.commits }} + 1)" >> $GITHUB_ENV
+
+      - uses: actions/checkout@v4
+        with:
+          # Ensure we can check out the pull request base in the script below.
+          fetch-depth: ${{ env.FETCH_DEPTH }}
+
+      - name: Set up Node
+        uses: actions/setup-node@v3
+        with:
+          node-version: '20'
+      - name: Install dependencies
+        run: |
+          yarn install
+
+      - name: Detect breaking changes
+        run: |
+          # Try to check out previous versions of the breaking change detection script. This ensures that
+          # we still detect breaking changes when entire files and their tests are removed.
+          git checkout "${{ github.event.pull_request.base.sha }}" -- ./scripts/detect-breaking-changes 2>/dev/null || true
+          ./scripts/detect-breaking-changes ${{ github.event.pull_request.base.sha }}
   agents_sdk:
     runs-on: 'ubuntu-latest'
     name: Detect Agents SDK regressions