fix(ci): use PR head SHA for concurrency group

github.sha is a temporary merge commit for pull_request events, so
push and pull_request for the same commit got different keys. Use
pull_request.head.sha (falls back to github.sha for push events)
to correctly deduplicate.

Author: wazolab

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ on:
     branches: [develop, main]
 
 concurrency:
-  group: ci-${{ github.sha }}
+  group: ci-${{ github.event.pull_request.head.sha || github.sha }}
   cancel-in-progress: true
 
 jobs: