fix: worktree detection

[zazer0]

Issue:

• multiple commands (list, resume, clean) would fail to detect worktrees
• this made aspects of the utility unusable - despite git worktree list showing them fine

Fix:

• there was an extra 'prefix' on the branch detection - removing this fixed it

Testing:

• Validated all commands (including resume) now work great! 🎉

P.S - thanks for making this utility @jlowin ! I've found it extremely useful already :))

[EmilRex]

@jlowin 👋 long time no see! Just wanted to upvote that I ran into the exact same issue and came here to open the exact same PR.