perf: v2.5.10 — ready for 10+ concurrent users, leaner locally

Measured on a copy of a real 1.2 GB / 253K-event database, 10 simulated
browsers + 10 hooks/s for 90 s: event-loop delay p99 1239 ms → 32 ms (max
2.0 s → 94 ms), 266 failed requests → 0, 74 → 111 requests/s served, server
RSS 633 → 346 MB. Entry bundle 975 KB raw → 394 KB (106 KB brotli).

Server
- /api/analytics: the events-table scans run in the read worker
  (scoped-stats eventAggregates, read-pool job analyticsEvents); runRead takes
  maxAgeMs — analytics 10 s, /api/workflows 30 s — keyed by the args
- /api/workflows/skill-usage: +event_type and a tool_name range instead of
  LIKE, so it uses idx_events_tool (784 ms → a few ms)
- idx_events_session_type_tool (session_id, event_type, tool_name,
  created_at) replaces idx_events_session_type: covering reads for session
  stats, the hook dedupes and the import resume point (1.2 s → 20 ms); 64 MB
  cache_size and 256 MB mmap_size on both connections
- WAL: the server sets wal_autocheckpoint = 0 and checkpoints PASSIVE every
  DASHBOARD_WAL_CHECKPOINT_MS (5 s) from the read worker's own writable
  connection; a failed checkpoint restores the automatic one (hook COMMIT p95
  109 ms → 15 ms at 100 hooks/s)
- tmux: one list-sessions answers a whole GET /api/lanes and the heal beat
  (liveSessions), shared for 1 s and cleared by this process's new/kill —
  GET /api/run's sync spawns had blocked 60 s of a 90 s run; the heal beat
  skips tmux when nothing runs; attach options chained into 2 spawns
- hooks: TurnDuration/APIError deduped against one read per hook instead of a
  query per transcript entry (23 ms/hook on a 763-turn session); one lane
  scan per hook; hourly upserts skip rows that did not grow; frames are sent
  after the transaction commits (and after the pane binding); new_event
  carries its row id; a split pane's (slot 1–9) hooks no longer rebind the
  lane's session_id
- watchdog liveness probe runs ps asynchronously; transcript newline scan via
  indexOf; startup subagent backfill fingerprints the files it already checked
- pty attach: backpressure (pause past 1 MB unsent, resume under 256 KB)
- static: hashed assets served from their pre-compressed .br/.gz sibling

Client
- hidden tabs neither refetch on WS events nor poll (useLiveRefresh, panes,
  lane cards, git header, changes panel, settings); no per-tab hourly
  /updates/check (the server already checks)
- refetch storms throttled (workspace tree/session list 3 s, /api/run only on
  a run-key change, notification pane lookup only when shown); WS reconnect
  jitter; terminal retry backoff 1.5 → 30 s, stops on 1008
- heavier throttles for aggregates (15 s) and detail views; Monitor keepIfSame;
  GET in-flight dedupe in request()
- lazy Dashboard/History, xterm (with the first terminal), lane modals, Sagi
  (only while enabled); only the active locale loads; Workspace chunk
  prefetched on a /workspace deep link
- Sagi: no work while disabled, pupil via CSS variables, memo avatar
- build: .br/.gz siblings, sourcemap hidden; service worker no longer caches
  /assets/ (cache v3 drops the old one)

Tests: scripts/test-server.js drops the GIT_DIR-family variables a hook
exports, so a suite run from a linked worktree's pre-commit can no longer
commit into the real repository or set core.bare.

Docs: ARCHITECTURE, DATABASE, API, DEPLOYMENT, client README,
docs/plans/perf/README.md (audit, checklist, results).

client/src/App.tsx

@@ -38,8 +38,8 @@
  * ## Internal dependencies
  * - `./components/Layout`
  * - `./components/SplashScreen`
- * - `./pages/Dashboard`
- * - `./pages/History`
+ * - `./pages/Dashboard` (lazy)
+ * - `./pages/History` (lazy)
  * - `./pages/SessionDetail` (lazy)
  * - `./pages/SettingsHub` (lazy)
  * - `./pages/Workspace` (lazy)
@@ -64,8 +64,6 @@ import { GlobalTooltip } from "./components/Tooltip";
 import { Toaster } from "./components/Toaster";
 import { ConfirmHost } from "./components/ConfirmHost";
 import { RouteErrorBoundary, reloadOnce } from "./components/RouteErrorBoundary";
-import { Dashboard } from "./pages/Dashboard";
-import { History } from "./pages/History";
 import { NotFound } from "./pages/NotFound";
 import { useWebSocket } from "./hooks/useWebSocket";
 import { useNotifications } from "./hooks/useNotifications";
@@ -75,7 +73,10 @@ import { reloadOnNewBuild } from "./lib/newBuildReload";
 import type { WSMessage } from "./lib/types";
 
 // The heavy pages (xterm, the diff viewer, the settings editors) load on first
-// visit instead of in the initial bundle.
+// visit instead of in the initial bundle — the Dashboard and History too, so the
+// entry chunk holds only the shell.
+const Dashboard = lazy(() => import("./pages/Dashboard").then((m) => ({ default: m.Dashboard })));
+const History = lazy(() => import("./pages/History").then((m) => ({ default: m.History })));
 const Workspace = lazy(() => import("./pages/Workspace").then((m) => ({ default: m.Workspace })));
 const SettingsHub = lazy(() =>
   import("./pages/SettingsHub").then((m) => ({ default: m.SettingsHub }))
@@ -156,8 +157,22 @@ export default function App() {
         <DocumentTitle />
         <Routes>
           <Route element={<Layout wsConnected={connected} />}>
-            <Route index element={<Dashboard />} />
-            <Route path="sessions" element={<History />} />
+            <Route
+              index
+              element={
+                <Page>
+                  <Dashboard />
+                </Page>
+              }
+            />
+            <Route
+              path="sessions"
+              element={
+                <Page>
+                  <History />
+                </Page>
+              }
+            />
             <Route
               path="sessions/:id"
               element={