bin/hack: worktree+claude automation

[nfgrep]

Closes #258

Sketch:

> bin/hack
Do you want to create a new branch or work on an existing one?
> new
What's the name of your new branch?
> foobar
Creating branch foobar...
Creating worktree at ../roast@foobar ...
Chdir into ../roast@foobar ...
Running claude ...

... do some coding with claude ...

> /exit
Are you done with the foobar worktree?
> yes
Chdir back to main worktree ...
Removing foobar worktree ...
Do you want to delete the foobar branch aswell?
> yes
Deleting foobar branch ...