fix: event-loop freezes, plugin-install boot crash, tmux attach/scrollbar, Codex transcripts

- GET /api/workflows: one LEAD() window pass in a read worker (read-pool.js,
  workflow-stats.js); idx_events_session restored, idx_events_tool added
- compat-sqlite gains function/pluck/readonly so a plugin install without a
  better-sqlite3 build boots again; antigravity-usage uses db.js's Database
- install-hooks adds no checkout hooks while the agenthub plugin is enabled
  (events were doubled)
- terminal attach runs the live tmux server's own binary; the pane scrollbar
  gets a visible 2-column style, and claude panes start with
  CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 so tmux keeps history to scroll
- Codex sessions' conversation in GET /api/sessions/:id/transcript
- Codex/Antigravity sessions claimed by their workspace without hooks
- UI-audit follow-ups, docs and OpenAPI

.env.example

@@ -91,6 +91,13 @@
 # (default: enabled).
 #   AGENTHUB_PRICING_SYNC=0
 
+# Heavy read-only aggregates (GET /api/workflows) run in a worker thread on
+# their own connection so they never stall other requests. 0 runs them inline
+# on the event loop instead (default: worker). A job past the timeout answers
+# 503 EREADTIMEOUT and the next one gets a fresh worker (default: 60000).
+#   AGENTHUB_READ_WORKER=0
+#   AGENTHUB_READ_TIMEOUT_MS=60000
+
 # Where settings saved from the dashboard persist (default:
 # $XDG_CONFIG_HOME/agenthub/settings.env, i.e. ~/.config/agenthub/settings.env).
 # Here or in the real environment; the file is located after this one loads.