feat: wire channel mode runtime config and docs

plugin/turn-manager.ts

@@ -11,7 +11,7 @@
  *   - If sender IS in turn order → current = next after sender
  */
 
-import { isMultiMessageMode, exitMultiMessageMode } from "./core/channel-modes.js";
+import { getChannelShuffling, isMultiMessageMode, markLastShuffled } from "./core/channel-modes.js";
 
 export type ChannelTurnState = {
   /** Ordered accountIds for this channel (auto-populated, shuffled) */
@@ -379,6 +379,7 @@ export function onSpeakerDone(channelId: string, accountId: string, wasNoReply:
     const newOrder = reshuffleTurnOrder(channelId, state.turnOrder, prevSpeaker);
     if (newOrder !== state.turnOrder) {
       state.turnOrder = newOrder;
+      markLastShuffled(channelId);
       console.log(`[dirigent][turn-debug] reshuffled turn order for channel=${channelId} newOrder=${JSON.stringify(newOrder)}`);
     }
   }