A terminal row published on `$SWARM.term.<hive>.<agent>` goes out bare,
with no envelope around it and no server-side stamp, so a subscriber had
nothing to place the row in time with beyond its own receipt clock —
wrong by the queue's latency and meaningless for anything read later
than live.
`TermMsg` gains `ts`, ISO 8601 UTC. `classify` takes the event's own
unix-seconds stamp and applies it to every row that event expands into,
so a row replayed out of sqlite says when it happened rather than when
it was read, and a row that sat in a lagging subscriber's buffer does
not lie about its time. The oversize degrade keeps it; only the body is
ever spent.
`TermEnvelope` stops duplicating `ts` and keeps `seq`: the dedup counter
is a real transport concern, the event's time is not, now that it rides
on the row. Nothing in the frontend read `envelope.ts` — only the type
declared it.
Refs #4321
053340128b