Statusline hook should verify file existence before modifications

Description

The statusline hook should check if the target file exists and read its contents before attempting to make modifications using the gh CLI.

Current Behavior

The hook appears to attempt modifications without first verifying the file exists or reading its current state.

Expected Behavior

The hook should:

1. Check if the file exists before attempting modifications
2. Read the current file contents
3. Then proceed with modifications based on the actual file state

Why This Matters

This would prevent potential errors and ensure the hook operates on actual file contents rather than making assumptions about file state.

Environment

• Platform: Linux
• OS Version: Linux 6.8.0-86-generic
• Claude Code: Latest version