fix: /stop leaves stale paired task, sawOutput guard, progress text overwrite

- /stop now resets the active paired task to completed so the next
  user message routes to the owner instead of the stuck reviewer
- Owner completion with sawOutput=false (e.g. interrupted by /stop)
  no longer auto-triggers the reviewer — treated as interrupted
- Clear pendingProgressText when intermediate updates arrive on an
  existing progress message, preventing flushPendingProgress from
  overwriting latestProgressText with stale buffered content

src/session-commands.ts

@@ -166,6 +166,7 @@ export async function handleSessionCommand(opts: {
 
   if (command === '/stop') {
     const killed = deps.killProcess();
+    deps.resetPairedTask?.();
     deps.advanceCursor(cmdMsg.timestamp);
     await deps.sendMessage(
       killed ? 'Agent stopped.' : 'No agent is currently running in this room.',