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/Workspace.tsx

@@ -85,6 +85,9 @@ import { endRuns } from "../lib/stopSession";
 import { ContextMenu, MenuItem, useContextMenu } from "../components/ContextMenu";
 import { confirmDiscard } from "../lib/confirm";
 import { keepIfSame } from "../lib/keepIfSame";
+import { laneChangeMatcher, runKeyOf } from "../lib/laneChange";
+import { sessionChangeMatcher } from "../lib/sessionChange";
+import { useLiveRefresh } from "../hooks/useLiveRefresh";
 import { useWorkLanes } from "../hooks/useLanes";
 import { LaneConsolePane } from "../components/run/LaneConsolePane";
 import {
@@ -1044,9 +1047,10 @@ export function Workspace() {
       .catch(() => undefined);
   }, []);
 
-  // Goes through `keepIfSame`: this fires every 5 s below, and a
-  // fresh-but-identical payload would otherwise re-render the lane strip, the
-  // lane card and the whole console area on every tick for nothing.
+  // Goes through `keepIfSame`: this re-reads on run-moving messages and a
+  // fallback poll below, and a fresh-but-identical payload would otherwise
+  // re-render the lane strip, the lane card and the whole console area for
+  // nothing.
   const refreshList = useCallback(() => {
     api.run
       .list()
@@ -1061,33 +1065,30 @@ export function Workspace() {
       window.dispatchEvent(new CustomEvent(LIVE_RUNS_EVENT, { detail: activeRuns.items }));
   }, [activeRuns]);
 
-  // Background poll so the run list and history reflect external changes
-  // (server-boot reconciliation, sibling tabs, direct DB edits) even when
-  // no WS event fires. Lighter than typical WS gaps; aggressive enough that
-  // status flips appear within seconds without needing a manual refresh.
+  // The run list follows the WebSocket instead of a blind 5 s poll: a pane
+  // starting, ending or learning its session in slot 0 moves the lane's run
+  // columns (`lane_update`); an agent starting in a free tab (slots 1–9)
+  // shows as a new session, one ending as a session status change, and a pane
+  // dying under its agent as `runs_interrupted`. This page's own starts, stops
+  // and a shown terminal's exit call `refreshList` directly
+  // (`onRunsChanged`). What none of those cover — a shell tab opened or closed
+  // from another browser, server-boot reconciliation — is caught by the
+  // 30 s fallback poll, on reconnect, and when the tab is shown or focused.
+  const [laneRunChanged] = useState(() => laneChangeMatcher(runKeyOf));
+  const [sessionRunChanged] = useState(() => sessionChangeMatcher((s) => `${s.status}`));
   useEffect(() => {
     refreshList();
-    const tick = setInterval(() => {
-      // Hidden tab: skip; the visibility handler below re-reads on show.
-      if (document.visibilityState === "visible") refreshList();
-    }, 5000);
-    return () => clearInterval(tick);
   }, [refreshList]);
-
-  // Refresh whenever the tab regains focus / visibility - typical when the
-  // user comes back from running `claude` in a terminal and wants to see the
-  // current state of every run without waiting for the next poll.
+  useLiveRefresh(refreshList, {
+    intervalMs: 30_000,
+    throttleMs: 1500,
+    match: (msg) =>
+      msg.type === "runs_interrupted" || laneRunChanged(msg) || sessionRunChanged(msg),
+  });
   useEffect(() => {
     const onFocus = () => refreshList();
-    const onVis = () => {
-      if (document.visibilityState === "visible") refreshList();
-    };
     window.addEventListener("focus", onFocus);
-    document.addEventListener("visibilitychange", onVis);
-    return () => {
-      window.removeEventListener("focus", onFocus);
-      document.removeEventListener("visibilitychange", onVis);
-    };
+    return () => window.removeEventListener("focus", onFocus);
   }, [refreshList]);
 
   const currentLane = selectedLaneId !== null ? lanes.find((l) => l.id === selectedLaneId) : null;