Clean Branches - Delete Merged Local Branches

Clean up local branches by checking their GitHub PR status and deleting those that have been merged.

Steps

1. Fetch and list branches — Fetch the latest remote state, then get all local branches except master:

git fetch origin master
git branch --format='%(refname:short)' | grep -v '^master$'

Show the list to the user. If no branches exist besides master, report that and stop.