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 when the current buffer already
matches the target source file.
Barrett Ruth
b7d6914dca