Adds an end-to-end integration test that runs the real pipeline against
live YouTube Atom feeds, verifying the merged feed is newest-first
across channels.
Refresh fetches 8 channel feeds concurrently and mirrors thumbnails to
disk so the offline feed still renders. Downloads are capped at 2 and
shell out to yt-dlp with an absolute binary path, since GUI apps do not
inherit a login shell PATH.
37 unit tests covering the three parsers and the database, including
that a feed refresh preserves download state and that a truncated
feed response fails rather than storing partial results.
Offline-first YouTube subscription feed reader: Takeout CSV import,
public Atom feeds for metadata, yt-dlp downloads constrained to
H.264/AAC for in-app WKWebView playback.
vincent