## Problem
`setup_problem` explicitly set `swapfile = true` on provisional buffers,
overriding the user's global `noswapfile` setting. The resulting `.swp`
files triggered E325 warnings on subsequent `:e` calls — especially
during the restore path, which redundantly re-opened the current buffer.
## Solution
Remove the `swapfile` override so the user's setting is respected, and
skip the `:e` call in `setup_problem` when the current buffer already
matches the target source file.
e674265527