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).

docs/DEPLOYMENT.md

@@ -263,8 +263,9 @@ AGENTHUB_CURSOR_DIR=                    # where Cursor keeps its data (default ~
 
 # Pricing and saved settings
 AGENTHUB_PRICING_SYNC=                  # 0|false|off disables automatic pricing from LiteLLM (default on)
-AGENTHUB_READ_WORKER=                   # 0 runs heavy aggregates (GET /api/workflows) inline instead of in the read worker (default worker)
+AGENTHUB_READ_WORKER=                   # 0 runs heavy aggregates (GET /api/workflows, /api/analytics' event scans) inline instead of in the read worker (default worker)
 AGENTHUB_READ_TIMEOUT_MS=60000          # a read-worker job past this answers 503 EREADTIMEOUT and gets a fresh worker
+DASHBOARD_WAL_CHECKPOINT_MS=5000        # WAL checkpoint from the read worker instead of inside a hook's COMMIT (0 = SQLite's automatic one)
 AGENTHUB_SETTINGS_FILE=                 # where dashboard-saved settings persist (default ~/.config/agenthub/settings.env);
                                         # load order: real env > the checkout's .env > this file
 
@@ -726,14 +727,22 @@ node --optimize-for-size server/index.js
 
 ### SQLite Tuning
 
-```javascript
-// server/db.js - Add these pragmas
-db.pragma('journal_mode = WAL');       // Write-Ahead Logging
-db.pragma('synchronous = NORMAL');     // Faster writes
-db.pragma('cache_size = -64000');      // 64MB cache
-db.pragma('temp_store = MEMORY');      // Temp tables in memory
-db.pragma('mmap_size = 30000000000');  // Memory-mapped I/O
-db.pragma('page_size = 4096');         // Optimal page size
+`server/db.js` already sets WAL, `synchronous = NORMAL`, a 64 MB `cache_size` and a
+256 MB `mmap_size`, and the server checkpoints the WAL from its read worker
+(`DASHBOARD_WAL_CHECKPOINT_MS`) instead of inside a hook's `COMMIT` — see
+[DATABASE.md § SQLite Pragmas](DATABASE.md#sqlite-pragmas). Nothing to add by hand.
+
+### Compression
+
+The client build writes a `.br` and a `.gz` beside every hashed asset, and the
+server sends the one the browser accepts (`Content-Encoding`, `Vary: Accept-Encoding`)
+— a first Workspace load is ~75 % smaller with no compression CPU at request time.
+API responses are not compressed by AgentHub; behind nginx, add:
+
+```nginx
+gzip on;
+gzip_types application/json;
+gzip_min_length 1024;
 ```
 
 ### Nginx Tuning