swarm: keep an agent's terminal rows and replay them on attach

swarm-controller now creates `term-main-<agent>` for every live agent, in
the same one-minute pass and with the same config style as
`term-sub-<agent>` (#4897): subjects `$SWARM.term.<agent>` only, max_age
24h, max_bytes 64 MiB, discard Old, max_message_size from the queue's
max_payload. An existing stream is opened as it is. The agent keeps its
plain publish on `$SWARM.term.<agent>` and gets no JetStream subject.

`GET /api/agents/{name}/term/stream` creates an ephemeral push consumer on
that stream starting 100 rows back, so a swarm-ui terminal opens with
recent history and then follows new rows, in order, from one
subscription. Each SSE event carries the row's stream sequence as its id,
and a reconnect's Last-Event-ID resumes after it. Without the stream the
route falls back to the live core subscription it used before.

The stream is `term-main-<agent>`, not `term-<agent>`: an agent may be
named `sub-x`, whose `term-<agent>` would be agent `x`'s subagent stream.
Its one literal subject cannot match `$SWARM.term.<agent>.sub.>`, which
needs more tokens, so the two streams never overlap.

The reader gains `$JS.API.CONSUMER.CREATE.*.*.$SWARM.term.*`, the
extended create form whose last tokens are the consumer's filter. Checked
against nats-server 2.14.4, the trailing `*` also admits a literal `*` or
`>` filter, so a consumer under it reaches any terminal row, main or
subagent; those are rows the reader already subscribes to and reads with
`STREAM.MSG.GET.*`.

Closes #4826

frontend/packages/swarm-ui/src/pages/agents/useSwarmTermStream.ts

@@ -3,9 +3,10 @@
 // `term_stream.rs`). Deliberately NOT `@hive/agent`'s `useLiveStream` —
 // that hook's wire shape is `TermEnvelope` (`{seq, msgs: []}`) plus a
 // history/backfill dance; the swarm relay forwards one bare `TermMsg`
-// per SSE event with no envelope and no history endpoint (a core NATS
-// subject, not `JetStream` — see `term_stream.rs`'s own module doc), so
-// there's nothing to buffer/dedupe/backfill against. Same row-coalescing
+// per SSE event, its replayed rows first and in order on the same
+// stream, so there's nothing to buffer/dedupe/backfill against. The
+// browser's own `Last-Event-ID` resumes a reconnect, so rows are kept
+// across one. Same row-coalescing
 // rule as `useLiveStream`'s `appendRow` (ported, not imported — one
 // small helper isn't worth a cross-package hop for).
 import { useEffect, useRef, useState } from "preact/hooks";