silence-kick removal: stop fanning removal announce to aro roster

Elazar mrivjlv3thm6: the silence-kick (agent removed from aro for received-N/sent-0) currently emits TWO legs — (1) DM to the REMOVED agent with rejoin path + object-to-PM, (2) an announce fanned to EVERY other aro member 'X removed from aro (silent: recv N sent 0)'. Leg 2 is pure record-keeping wasting a full-context turn on each roster member for a fact none must act on. FIX: keep leg 1 (removed agent needs rejoin notice), DROP leg 2 entirely. Peers discover the departure lazily — a DM to the removed agent no longer fans to it. Do NOT replace with an aro-fanout to a passive room; just suppress. (This is the hub obeying its own recipient-action-gate / Rule 9.) coder: find the silence-kick emit site, bring the exact before/after + confirm no other consumer depends on the member-broadcast. Audit via audit-llmmsgsrv-ca; I gate+bounce.