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.

client/src/components/SessionRowMenu.tsx

@@ -11,9 +11,26 @@
 import { useTranslation } from "react-i18next";
 import { useNavigate } from "react-router-dom";
 import { ContextMenu, MenuItem, MenuSeparator, type MenuPoint } from "./ContextMenu";
+import { copyText } from "../lib/clipboard";
 
 export type SessionRowRef = { id: string; lane_id?: number | null; cwd?: string | null };
 
+/**
+ * Where "Open in workspace" goes for a session: its live pane when a dashboard
+ * run holds it (`&run=`), else its workspace's replay (`&session=`); null when
+ * no workspace owns it.
+ */
+export function workspaceHref(
+  session: SessionRowRef,
+  runs: ReadonlyArray<{ id: string; laneId: number | null; sessionId: string | null }> = []
+): string | null {
+  const run = runs.find((r) => r.sessionId === session.id && r.laneId != null);
+  if (run) return `/workspace?lane=${run.laneId}&run=${encodeURIComponent(run.id)}`;
+  if (session.lane_id != null)
+    return `/workspace?lane=${session.lane_id}&session=${encodeURIComponent(session.id)}`;
+  return null;
+}
+
 export function SessionRowMenu({
   session,
   x,
@@ -26,7 +43,7 @@ export function SessionRowMenu({
     onClose();
     fn();
   };
-  const copy = (text: string) => pick(() => void navigator.clipboard.writeText(text));
+  const copy = (text: string) => pick(() => void copyText(text));
 
   return (
     <ContextMenu x={x} y={y} onClose={onClose} testId={`session-row-menu-${session.id}`}>
@@ -34,11 +51,7 @@ export function SessionRowMenu({
         {t("menu.details")}
       </MenuItem>
       {session.lane_id != null && (
-        <MenuItem
-          onSelect={pick(() =>
-            navigate(`/workspace?lane=${session.lane_id}&session=${encodeURIComponent(session.id)}`)
-          )}
-        >
+        <MenuItem onSelect={pick(() => navigate(workspaceHref(session)!))}>
           {t("menu.inWorkspace")}
         </MenuItem>
       )}