perf(client): cut needless polling for local users

- ConversationView: an ended session (SessionDetail, SessionReplay pass
  `ended`) polls its transcript every 60 s instead of 3 s and stops
  rescanning sub-agents; new_event, reconnect and show still fetch at once.
- Workspace: GET /api/run follows run-moving WS messages (lane run
  columns, session created/status change, runs_interrupted) with a 30 s
  fallback, instead of a blind 5 s poll.
- StatusBar: session counts re-read only when a session's
  status/waiting/archived state changes (60 s fallback); costs re-read at
  most every 30 s while work is happening and every 2 min otherwise.
- Dashboard recent activity: 60 s safety poll (was 10 s) plus remote
  import messages; WS still prepends new events.
- New lib/sessionChange.ts matcher with tests.

client/src/pages/SessionDetail.tsx

@@ -1129,7 +1129,11 @@ export function SessionDetail() {
 
       {visitedTabs.has("conversation") && (
         <div hidden={activeTab !== "conversation"}>
-          <ConversationView sessionId={session.id} initialTranscriptId={pendingTranscriptId} />
+          <ConversationView
+            sessionId={session.id}
+            initialTranscriptId={pendingTranscriptId}
+            ended={session.status !== "active"}
+          />
         </div>
       )}