* feat: add git-delete-gone-branches command
Adds a new command to delete local branches whose remote-tracking
branch has been deleted (shown as [gone] in git branch -vv).
This is a common need after PRs are merged and remote branches are
cleaned up, leaving stale local branches behind.
Features:
- Deletes all local branches with a gone remote in one command
- --dry-run / -n flag to preview branches before deletion
Closes#1220
* Address PR review feedback on git-delete-gone-branches
- Use git for-each-ref instead of git branch -vv to avoid false
positives from commit messages containing ': gone]'
- Add interactive confirmation prompt by default; skip with -f/--force
- Add -p/--prune flag to run git fetch --prune before checking
- Add generated man page .1 and .html files
* Use GitHub profile for author contact in man page
* Fix gone-branch detection with nobracket format
