CrewBus Desktop v0.1.20

Hotfix release: v0.1.19 shipped a dashboard-breaking SyntaxError (command-palette label escape evaluated server-side, killing the entire client script at parse time for every web/desktop user). This build carries the one-line fix plus a regression test that syntax-checks the rendered client script.

Sidecar core is otherwise identical to v0.1.19 (Briefs view, /api/gather, task-scoped rosters, presence/merge/observability fixes).

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