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/main.tsx

@@ -1,8 +1,8 @@
 /**
  * @file main.tsx
- * @description Vite client entry point. Bootstraps React 18, loads global styles
- * and i18n, registers the service worker for offline asset caching, and mounts
- * {@link App} into `#root`.
+ * @description Vite client entry point. Bootstraps React 18, loads global styles,
+ * registers the service worker, prefetches the Workspace chunk on a `/workspace`
+ * deep link, and mounts {@link App} into `#root` once the active locale is loaded.
  *
  * ## Fonts
  * Only Latin subsets of Inter and JetBrains Mono are imported so Vite bundles
@@ -63,7 +63,10 @@ import "@fontsource/jetbrains-mono/latin-500.css";
 import "@fontsource/jetbrains-mono/vietnamese-400.css";
 import "@fontsource/jetbrains-mono/vietnamese-500.css";
 import App from "./App";
-import "./i18n";
+import { i18nReady } from "./i18n";
+// Deep link into the Workspace: start its (lazy) chunk now, in parallel with the
+// locale fetch below, instead of after the first render asks for it.
+if (location.pathname.startsWith("/workspace")) void import("./pages/Workspace");
 import "./index.css";
 
 if ("serviceWorker" in navigator) {
@@ -93,8 +96,14 @@ if ("serviceWorker" in navigator) {
 const root = document.getElementById("root");
 if (!root) throw new Error("Root element not found");
 
-createRoot(root).render(
-  <StrictMode>
-    <App />
-  </StrictMode>
-);
+// The active locale is a lazy chunk: render once it is in, so no raw key ever
+// paints. A failed fetch still renders (i18next falls back to the keys).
+void i18nReady
+  .catch(() => undefined)
+  .then(() =>
+    createRoot(root).render(
+      <StrictMode>
+        <App />
+      </StrictMode>
+    )
+  );