Page an answer larger than one message of the bus, and keep overviews brief (hq issue 314)

The client library refuses to send a reply over the bus's max_payload, and the
controller only logged it: conditions and status answered nobody for hours on
2026-10-08 while calls said each was answered in 130 ms, and the operator's
channel read nothing. An answer too large is now held under its call and paged
to the caller that asks, on the same subject; a caller that does not page is
told in words, and calls says it. The overviews no longer carry every finding:
conditions and status list each condition with its newest evidence, doctor at
most twenty findings a probe (probe= gives one whole), and the JSON overviews
are sent once, as data, instead of twice.

internal/link/seattools.go

@@ -69,10 +69,18 @@ func (b OverNATS) serveTools(seat string, subjectOf func(string) string, handler
 		subject := subjectOf(verb)
 		bind := func() (*nats.Subscription, error) {
 			return b.Conn.QueueSubscribe(subject, "seat."+seat, func(msg *nats.Msg) {
+				if msg.Header != nil && msg.Header.Get(PageHeader) != "" {
+					// A part of an answer too large for one message, asked by the caller it was paged
+					// to (novox/hq issue 314): not a call of its own.
+					go Calls.servePage(seat, verb, msg, logger)
+					return
+				}
 				// Its own goroutine per call: a slow `push` must not hold up a `status` asked beside it,
 				// and the library would otherwise run handlers one after another. Answered once, within
-				// AnswerWithin, and kept (novox/hq issue 265).
-				go Calls.serveCall(seat, verb, json.RawMessage(msg.Data), msg.Reply, handle, msg.Respond, logger)
+				// AnswerWithin, and kept (novox/hq issue 265). Within what the bus carries in one
+				// message, or paged (issue 314).
+				go Calls.serveCallWithin(seat, verb, json.RawMessage(msg.Data), msg.Reply, handle, msg.Respond,
+					b.Conn.MaxPayload(), logger)
 			})
 		}
 		sub, err := bind()