ci: add schema drift check to PR quality gates

Author: Hweinstock

.github/workflows/lint.yml

@@ -100,3 +100,28 @@ jobs:
           path: node_modules
           key: node-modules-${{ hashFiles('package-lock.json') }}
       - run: npm run typecheck
+
+  schema-check:
+    needs: setup
+    if: ${{ !startsWith(github.head_ref, 'release/') }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        with:
+          node-version: 20.x
+      - uses: actions/cache/restore@v5
+        with:
+          path: node_modules
+          key: node-modules-${{ hashFiles('package-lock.json') }}
+      - run: npm run build
+      - run: node scripts/generate-schema.mjs
+      - name: Check for schema drift
+        run: |
+          if ! git diff --exit-code schemas/; then
+            echo ""
+            echo "❌ JSON schema is out of date with Zod source schemas."
+            echo "Run 'npm run build && node scripts/generate-schema.mjs' and commit the result."
+            exit 1
+          fi
+          echo "✓ JSON schema is up to date"