ci(build): let a running main build finish before the next push's build starts

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.github/workflows/build.yml

@@ -33,7 +33,7 @@ permissions:
 
 concurrency:
   group: build-${{ github.event_name }}-${{ github.event.pull_request.number || inputs.pr || github.ref }}
-  cancel-in-progress: true
+  cancel-in-progress: ${{ github.event_name != 'push' }}
 
 env:
   CONFIGURE: >-