CrewBus Desktop v0.1.19

Bundled sidecar core picks up the multi-brief management release:

• Dashboard Briefs view: one row per fan-out (subject, workers, checkpoint/final counts, acked fraction, last activity); click for the gathered thread. New GET /api/gather endpoint; Crews brief/groups column; Recent activity text filter + checkpoint/final toggle.
• Spawn rosters are task-scoped: unrelated concurrent briefs collapse to a count instead of leaking names cross-task.
• Mobile 0.6.0 (separate Expo track): live worker counts, brief-grouped Triage, Briefs screen, foreground approval/dead-man watcher.

Installs update via the signed updater once CI finishes building the per-OS bundles below.