Fork Conversation always creates a new worktree

Forking conversation is very useful to try out different ideas, but these don't always include code changes and having to wait minutes for a new worktree creation is very annoying, and it is hard to merge the changes back to the original branch.

Please let me choose, I should be able to just for the conversation on the same directory

Start by tracing the Fork Conversation flow and where it creates a new worktree. Determine how the user can choose between the current directory and a new worktree; done means conversation forks can use the selected location without forcing unnecessary worktree creation.

Written by the indexing model from the issue text.