ci: Add workflow concurrency configuration

Author: Copilot

.github/workflows/build.yml

@@ -2,6 +2,10 @@ name: Build
 
 on: [push, pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 permissions:
   contents: read