feat: parent branch selection

[ArtificialPB]

Adds support for selecting which parent branch to use when branching off the worktrees.

Branch selection pane uses fuzzy search so it's easy to filter the branches:

Instances now also show the parent branch:

[github-actions]

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[ArtificialPB]

I have read the CLA Document and I hereby sign the CLA

[mufeez-amjad]

Thanks for this PR – I was just thinking about this yesterday 😄

[matthew-petty]

I implemented something similar in #211 for my personal workflow. My implementation doesn't use state or popops and doesn't allow an arbitrary branch. I think I might like your implementation better.

One thing I did in #211 that I like is adding m as a new hotkey to create from main, as well as a new config to specify a custom name for the default branch if you use a different name.

[TeddyHarnat]

Any chance this is getting merged in, or is this project stale?