UI shows stale diff after branch merge and deletion

Bug Description

After merging a PR and deleting the feature branch locally, the Claude Code UI continues to show a stale diff indicator (main ← main with +11 -11) even though git status confirms the working tree is clean and up to date with origin/main.

Steps to Reproduce

1. Create a feature branch from main, make changes, commit, and push
2. Create a PR and merge it into main
3. Switch back to main and git pull (fast-forward merge succeeds)
4. Delete the local feature branch with git branch -d <branch>
5. Run git status — confirms clean working tree on main, up to date with origin/main
6. The Claude Code UI still shows main ← main with the diff count from the now-merged branch

Expected Behavior

The diff indicator should clear after the branch is merged and the local state is clean.

Actual Behavior

The UI continues to display +11 -11 and main ← main despite no actual diff existing.

Environment

• Platform: macOS (Darwin 25.3.0)
• Claude Code: CLI / Desktop app

🤖 Generated with Claude Code