feat(dashboard): lazy routes, Needs-you strip, URL state, exact numbers

- Workspace, SettingsHub, SessionDetail and the Workflow sub-tab are lazy
  (main bundle 2,166 kB -> ~920 kB), wrapped in RouteErrorBoundary: a stale
  chunk after a self-update reloads once (vite:preloadError too), any other
  error shows a Reload panel instead of a blank page.
- Live refresh: lib/throttle.ts + hooks/useLiveRefresh.ts replace trailing
  debounces that froze under a steady event stream; refresh skips hidden
  tabs and refetches after a WebSocket reconnect. Monitor loads only while
  shown, with one batched GET /api/agents?session_ids= instead of N+1; a
  failing endpoint is an inline error, not a blank Dashboard.
- NeedsYouStrip on Monitor and above Analytics. Tabs, filters, page, sort
  and search live in the URL (Dashboard, Sessions, Activity, SessionDetail).
- Sessions: tool / workspace / date-range filters, CSV/JSON export
  (formula-neutralised), focusable row links, Open in workspace (the dead
  /run links are gone), stale responses dropped, error + Retry.
- Fixes: "NaNs" durations, 30/7-day charts skipping idle days, weekday
  labels west of UTC (now averages), cache hit rate denominator, billable
  tokens vs cache reads, exact tool-call counts, "To" date = end of day,
  invalid ?from= no longer throws, recent list no longer shrinks to 15,
  stable message keys, transcript switch races.
- Light-theme-unreadable bg-black code panels and dark-only DAG fills use
  tokens; status configs and chart colours use theme tokens; Health tab
  and other literals translated.
- Server (additive): GET /api/agents?session_ids=, GET /api/sessions
  awaiting=1&from=&to=, stats tool_call_count/distinct_tool_count, event
  rows carry session/agent labels.

server/routes/events.js

@@ -102,7 +102,15 @@ router.get("/", (req, res) => {
 
   const { sql: whereSql, params: whereParams } = buildWhere(filters);
 
-  const listSql = `SELECT * FROM events ${whereSql} ORDER BY created_at DESC, id DESC LIMIT ? OFFSET ?`;
+  // Labels for the row (session name/cwd, agent name/type) come with it, so a
+  // list page never downloads every session and agent just to name them.
+  const listSql = `SELECT events.*,
+      (SELECT name FROM sessions WHERE id = events.session_id) as session_name,
+      (SELECT cwd FROM sessions WHERE id = events.session_id) as session_cwd,
+      (SELECT lane_id FROM sessions WHERE id = events.session_id) as session_lane_id,
+      (SELECT name FROM agents WHERE id = events.agent_id) as agent_name,
+      (SELECT subagent_type FROM agents WHERE id = events.agent_id) as agent_subagent_type
+    FROM events ${whereSql} ORDER BY created_at DESC, id DESC LIMIT ? OFFSET ?`;
   const countSql = `SELECT COUNT(*) as count FROM events ${whereSql}`;
 
   const events = db.prepare(listSql).all(...whereParams, limit, offset);