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/sessions.js

@@ -193,6 +193,23 @@ router.get("/", (req, res) => {
     );
     params.push(Number(lane), Number(lane));
   }
+  // `awaiting=1` = only sessions blocked on the user (an active session with
+  // `awaiting_input_since`), the UI's "Waiting" filter, done before the limit.
+  if (req.query.awaiting === "1") {
+    where.push("s.awaiting_input_since IS NOT NULL AND s.status = 'active'");
+  }
+  // `from`/`to` (ISO) bound `started_at`; an unparseable value is ignored.
+  for (const [key, op] of [
+    ["from", ">="],
+    ["to", "<="],
+  ]) {
+    const raw = req.query[key];
+    const d = typeof raw === "string" && raw ? new Date(raw) : null;
+    if (d && !Number.isNaN(d.getTime())) {
+      where.push(`s.started_at ${op} ?`);
+      params.push(d.toISOString());
+    }
+  }
   // `archived=0|1` = only live / only archived; absent = both, as before.
   if (req.query.archived === "0") where.push("s.archived_at IS NULL");
   if (req.query.archived === "1") where.push("s.archived_at IS NOT NULL");
@@ -330,6 +347,9 @@ router.get("/:id/stats", (req, res) => {
   const totalEvents = stmts.sessionEventCount.get(sessionId)?.count ?? 0;
   const eventsByType = stmts.sessionEventTypeCounts.all(sessionId);
   const tools = stmts.sessionToolUsageCounts.all(sessionId);
+  // Exact totals: `tools_used` is a top-15 list, so its sum is not the count.
+  // A tool call is a PreToolUse; a session with none (imported) counts PostToolUse.
+  const toolTotals = stmts.sessionToolCallTotals.get(sessionId) || {};
   const errors = stmts.sessionErrorCount.get(sessionId)?.count ?? 0;
   const timeRange = stmts.sessionEventTimeRange.get(sessionId) || {};
   const subagentTypes = stmts.sessionAgentTypeCounts.all(sessionId);
@@ -370,6 +390,8 @@ router.get("/:id/stats", (req, res) => {
     total_events: totalEvents,
     events_by_type: eventsByType,
     tools_used: tools,
+    tool_call_count: toolTotals.pre > 0 ? toolTotals.pre : (toolTotals.post ?? 0),
+    distinct_tool_count: toolTotals.distinct_tools ?? 0,
     error_count: errors,
     first_event_at: timeRange.first_at ?? null,
     last_event_at: timeRange.last_at ?? null,