Is there a reason why metadata and the message are stored so separately? I.e. why

   INBOX/2023-09-04_13:47_builds@sr.ht,GTfrlwJfN5vyR28R
   INBOX/.meta/GTfrlwJfN5vyR28R.flags

instead of

   INBOX/2023-09-04_13:47_builds@sr.ht,GTfrlwJfN5vyR28R/message
   INBOX/2023-09-04_13:47_builds@sr.ht,GTfrlwJfN5vyR28R/.flags

The latter structure would allow creating/deleting the message and flags atomically.