bug: `<file>.new` buffer persists after edit request diff

Describe the bug

When we display a diffpatch in response to an edit request, Neovim creates a <file>.new buffer. Even after the diff is closed, the .new buffer appears in e.g. buffer and file pickers, which is confusing and noisy.

Steps To Reproduce

1. vim.g.opencode_opts.events.permissions.edits.enabled = true
2. ask opencode to edit a file
3. Respond to the edit request via the diff tab (haven't checked whether this only happens with certain responses)

Expected Behavior

<file>.new should be deleted from the buffer list.

See plugin/events/permissions/edits.lua