The Desktop delivers each target's claimed envelopes in the order the drain returns them, one
turn at a time, and says so at the call site; the user guide states the same guarantee
("messages to the same Bot are delivered in order, one turn at a time"). The claim sorted the
outbox directory by filename, which is uuid4().hex — so the order handed to the Desktop was
random, and a sender's second instruction to one agent could be delivered before its first.
Sort by the mtime _sweep_stale already treats as an envelope's age, with the name only breaking
ties. The whole-second created_at field cannot separate two DMs sent in the same second.
The test forces the filenames into the reverse of the send order, which random ids reproduce
half the time: it fails on the filename sort, on newest-first, and when the mtime is dropped.
135bf07a75