CI: run test workflow on feature branches

Add claude/** branches to push trigger so the test job runs on
feature branch pushes. Docker Hub push remains gated to master only.

https://claude.ai/code/session_01MukmmJhsNvpwRmVAqAQvd8

Author: claude

.github/workflows/docker.yml

@@ -4,7 +4,7 @@ on:
   workflow_dispatch:
 
   push:
-    branches: ["master"]
+    branches: ["master", "claude/**"]
 
   schedule:
     - cron: "0 8 * * 1"