Marking mail as spam (or not spam) updated the email list but nothing
else, unlike delete/move which patch the folder counters optimistically.
Without a connected JMAP push the sidebar badges simply never moved, and
"not spam" additionally left the reading pane stuck on the message that
had just left the folder.
markAsSpam now mirrors moveToMailbox: source folder counts down, junk
counts up (honoring that trash-and-read delivers the mail to junk
already read). batchMarkAsSpam and batchUndoSpam mirror the batch move
pattern the same way.
undoSpam advances the selection to the next message like markAsSpam
already did, and refreshes the mailbox list instead of patching counts:
in the undo-toast path the email is no longer in the list, so its unread
state is unknown and an optimistic patch is not possible.
