chore: add concurrency control to publish workflow

- Add concurrency group with cancel-in-progress enabled
- Prevents multiple publish runs for the same ref
- Matches configuration used in CI workflow

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: vinta

.github/workflows/publish.yml

@@ -8,6 +8,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   publish:
     runs-on: ubuntu-latest