SQSCANGHA-144 Add gate jobs to QA workflows for branch protection

Add a non-matrix gate job to qa-main, qa-deprecated-c-cpp, and
qa-install-build-wrapper workflows. Each gate job depends on all
other jobs in its workflow and provides a single stable check context
that can be used in GitHub branch protection required status checks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/qa-deprecated-c-cpp.yml

@@ -88,3 +88,17 @@ jobs:
           BINARY: ${{ steps.run-action.outputs.build-wrapper-binary }}
         run: |
           ("$BINARY" || true) | grep "build-wrapper, version "
+
+  qa-gate:
+    name: QA Deprecated C and C++ - gate
+    runs-on: ubuntu-latest
+    needs: [output-test]
+    if: always()
+    steps:
+      - name: Check all jobs passed
+        run: |
+          if [[ "${{ contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled') }}" == "true" ]]; then
+            echo "One or more required jobs failed or were cancelled."
+            exit 1
+          fi
+          echo "All checks passed."