docs(althing): operator ruling — leave pre-deploy seats on their old channel

Eight of seventeen live seats were still on fifo after the 3.3.1 deploy,
because a SessionStart hook cannot reach a session that was already running.
Operator's call: leave them. They are reachable, mail is held at the post
office regardless, and each self-corrects at its next session start; the
residual is that a reaped fifo waiter goes silent until restart, which costs
timeliness and never mail.

Recorded with the no-unsolicited-fleet-notification directive next to it,
since the tempting action here is precisely the prohibited one — audit,
report the count, let the operator decide.

docs/runbooks/althing-deploy.md

@@ -157,6 +157,29 @@ The 2026-09-01 lesson was *compare the hook list, not the version string*. This
 is the same lesson one turn deeper: here the hook list was identical too, and
 only the file contents moved.
 
+## A seat already running when the plugin lands never auto-declares — leave it
+
+The SessionStart hook fires at session start and nowhere else, so any session
+that was already running when a plugin deploy landed keeps its old channel
+until it restarts. After the 3.3.1 deploy that was **eight of seventeen live
+seats**, all still on `fifo`.
+
+**Operator ruling 2026-09-02: leave them.** They are reachable now, the post
+office holds mail regardless, and each self-corrects at its next session start.
+The residual exposure is that a fifo waiter is what Claude Code 2.1.257 reaps —
+one seat was reaped three times in a morning — and a reap converts a healthy
+seat into a silent one until the next restart. That costs timeliness, never
+mail.
+
+⚠ **Do not mass-message the affected seats.** Standing operator directive: no
+unsolicited fleet notification, ever, unless asked. Direct correspondence with
+a counterparty about work in hand is fine; sweeping the handle list is not.
+Audit it, report the count, and let him decide — as he did here.
+
+The one-liner, for a seat that asks or an operator who wants one moved:
+
+    althing-route declare --discover-pid
+
 ## ⚠ The `cc` channel is an undocumented interface, taken deliberately
 
 From 3.3.0 a Claude Code seat is poked over its own message socket