Add separate UI Lab scenarios for true first-run onboarding and post-update What's New checks. Keep empty-library fixtures reusable across mock data, tagger readiness, worker pause defaults, and launch-time version state so browser verification can exercise the real flows.
Add a UI-Lab-only (mode === "ui", dead-code-eliminated from real builds)
URL override for the What's New modal: ?changelog=unreleased shows the
in-progress notes before they ship, ?changelog=small serves a synthetic
hotfix-sized entry to exercise the compact layout (including a no-lead
bullet), and ?changelog=<version> previews any released entry. Documented
in docs/ui-lab.md alongside the ?scenario= table.
Add a dev-only Vite UI mode with Tauri API mocks, in-memory fixture scenarios, reusable media source handling, and documentation for browser-based visual testing.
LyAhn