Adds a live presence layer so the Settings → Team members roster and the
inbox Assign dropdown show who is actively using the dashboard, idle, or
gone. Implements #269.
How it works
- New `member_presence` table + `touch_presence` SECURITY DEFINER RPC
(migration 024). Account-scoped SELECT RLS mirrors the read-only
roster; the RPC derives account_id server-side, never client-supplied.
- The active client heartbeats 'online'/'away' every ~30s; 'offline' is
derived by viewers from staleness, so a closed tab resolves to offline
without an unreliable unload write.
- Pure, unit-tested derivation/formatting in src/lib/presence.ts.
- `usePresence` reads the table, subscribes to Realtime (subscribe-then-
merge so events landing mid-fetch aren't clobbered), and re-derives
offline on a 15s tick.
- Roster: avatar badge + tooltip + "N online · N away · N offline"
summary, with an aria-label so AT/keyboard users get presence too.
Inbox Assign dropdown: matching dot before each teammate.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
