Walk all YouTube sources fully; channel order is not newest-first

The Iron Culture channel lists recent episodes mid-list (Ep 392/393 at
~position 360 of 396), so the 'channels enumerate newest-first' boundary
assumption is wrong: with it, rssd would break at the first pre-start-date
video and miss recent episodes, while re-resolving a boundary video every
poll. Walk channels exactly like playlists: always record out-of-range
videos as skipped so discovery stays incremental.

Also ignore media files (manual yt-dlp downloads have landed in the
working tree before).

.gitignore

@@ -0,0 +1,6 @@
+
+# Podcast download byproducts
+*.webm
+*.mp4
+*.opus
+*.mp3

main.go

@@ -175,11 +175,6 @@ func pollYouTube(feed config.Feed, sm *state.Manager, jobs chan<- downloader.Dow
 	})
 
 	start := feed.PublishedAt()
-	// Channels enumerate newest-first, so the first video older than the start
-	// date is a stable boundary: everything after it is older too. Playlists
-	// have no guaranteed order, so they must be walked fully and their
-	// out-of-range videos recorded as skipped to avoid re-resolving them.
-	newestFirst := !strings.Contains(strings.ToLower(feed.URL), "list=")
 
 	newCount, enqueued, skipped := 0, 0, 0
 	// Per-video resolve timeout. A single pathological video (JS-challenge
@@ -200,16 +195,12 @@ func pollYouTube(feed config.Feed, sm *state.Manager, jobs chan<- downloader.Dow
 			continue
 		}
 
-		// Out of the start_date window.
+		// Out of the start_date window. Record as skipped so it isn't
+		// re-resolved next poll. (Channel video order is not reliably
+		// newest-first — e.g. the Iron Culture channel lists recent episodes
+		// mid-list — so we can't stop at the first out-of-range video and
+		// must walk the whole source.)
 		if !start.IsZero() && !info.UploadDate.IsZero() && info.UploadDate.Before(start) {
-			if newestFirst {
-				// Stop at the first out-of-range video without recording it. It
-				// stays "new" each poll, so it remains a stable boundary and we
-				// never walk backward through older videos.
-				fmt.Fprintf(os.Stderr, "rssd: %s reached pre-start-date boundary, stopping\n", feed.URL)
-				break
-			}
-			// Playlist: record as skipped so it isn't re-resolved next poll.
 			dp := computeYTDestPath(feed.OutputDir, info.UploadDate, info.Title, v.ID)
 			if sm.AddJobWithStatus(feed.URL, watchURL(v.ID), dp, state.StatusSkipped, info.Duration) {
 				skipped++