* prune merged branches
* interactively prompt for prune
* delete remote tracking ref too
* disable selecting merged branches in TUIs
* include full list (including merged PRs) in PUT request to stacks API
* add prune to docs
* addressing review comments
* increment skill file version
* switch cmd to interactively switch to another branch in the stack
* add switch to docs
* addressing review comments
* bump skill file version
* default to current branch