Handle slug changes more elegantly #61

Sometimes I will change the title of a query in stmo and then fetch the change locally. This generates a duplicate of the query file with the new slug. Eventually Claude notices and decides to delete one of them. Sometimes it chooses the wrong one 😱.

The ideal would be just automatically removing the old query, but unless we know that that version has already been deployed there is a risk of losing changes. So I'm not exactly sure what the right fix is here. Perhaps some flow where stmo-cli suggests that Claude ask the user if they want to remove the old one?