CI: trigger on push to default branch (main, master, claude/**)

Also run PR checks for PRs targeting any of these branches.

https://claude.ai/code/session_015LpmjAt17XD582hZ9TPLCv

Author: claude

.github/workflows/ci.yml

@@ -2,9 +2,9 @@ name: CI
 
 on:
   push:
-    branches: [ main, 'claude/**' ]
+    branches: [ main, master, 'claude/**' ]
   pull_request:
-    branches: [ main ]
+    branches: [ main, master, 'claude/**' ]
 
 permissions:
   contents: read