Add 4 more video-guide clips covering core new-user onboarding

connect-decoder, add-drivers-cars, create-race, and run-a-session join the 3 existing
tab-focused clips, so the video guides now cover the actual first-run path a new user
hits, not just this session's UI restructuring.

record-video-guides.mjs gained a prepare() hook (for clips needing a live dependency,
like a fake decoder socket, before the app is seeded) and a clickNav() helper that
exercises the app's real client-side navigation instead of a full page reload, so
switching views in a clip looks like the smooth transition a real user sees.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "rc-racecore",
-  "version": "1.18.2",
+  "version": "1.19.0",
   "private": true,
   "description": "RC RaceCore live timing and race control with AMMC ingest and SQLite persistence",
   "engines": {