refactor: remove all playlist support, fix message ordering

- Remove playlist handler, keyboard, and all related callback routing
- Strip playlist parameter from YouTube Music radio URLs, reject pure playlists
- Send media preview before format selection prompt (correct ordering)
- Remove DetectPlaylist/GetPlaylistInfo methods (no longer needed)
- Remove IsPlaylist, PlaylistCount, PlaylistEntries from MediaInfo
- Remove PlaylistState struct, keep PlaylistEntry for search results
- Update README to reflect removal of playlist feature

internal/dl/ytdlp.go

@@ -151,19 +151,11 @@ func (c *Client) GetMediaInfo(url string) (*domain.MediaInfo, error) {
 	}
 
 	mi := &domain.MediaInfo{
-		URL:        url,
-		Title:      info.Title,
-		Uploader:   info.Uploader,
-		Thumbnail:  info.Thumbnail,
-		Duration:   info.Duration,
-		IsPlaylist: info.Playlist != "",
-	}
-
-	if mi.IsPlaylist {
-		mi.PlaylistCount = info.PlaylistCount
-		mi.PlaylistEntries = c.parsePlaylistEntries(info.Entries)
-		c.setCache(url, mi)
-		return mi, nil
+		URL:       url,
+		Title:     info.Title,
+		Uploader:  info.Uploader,
+		Thumbnail: info.Thumbnail,
+		Duration:  info.Duration,
 	}
 
 	langSet := make(map[string]bool)
@@ -171,8 +163,6 @@ func (c *Client) GetMediaInfo(url string) (*domain.MediaInfo, error) {
 	for _, f := range info.Formats {
 		ff := c.convertFormat(f)
 		mi.Formats = append(mi.Formats, ff)
-		// Only consider languages from formats with audio or video to avoid
-		// prompting for subtitle-only or auto-generated caption languages.
 		if (ff.HasAudio || ff.HasVideo) && ff.Language != "" && !langSet[ff.Language] {
 			langSet[ff.Language] = true
 			mi.Languages = append(mi.Languages, ff.Language)
@@ -187,68 +177,6 @@ func (c *Client) GetMediaInfo(url string) (*domain.MediaInfo, error) {
 	return mi, nil
 }
 
-// GetPlaylistInfo fetches a flat playlist listing (fast, no format detail).
-func (c *Client) GetPlaylistInfo(url string) (*domain.MediaInfo, error) {
-	if cached := c.getCached(url); cached != nil {
-		slog.Debug("cache hit", "url", url)
-		return cached, nil
-	}
-
-	isPlaylist, mi, err := c.DetectPlaylist(url)
-	if err != nil {
-		return nil, err
-	}
-	if !isPlaylist {
-		mi.IsPlaylist = false
-		mi.PlaylistCount = 0
-		mi.PlaylistEntries = nil
-	}
-
-	c.setCache(url, mi)
-	return mi, nil
-}
-
-// DetectPlaylist runs a fast flat yt-dlp check to determine if the URL is a playlist.
-// It returns basic info without format details. For non-playlist URLs it returns false.
-// Does NOT cache the result so a subsequent GetMediaInfo call fetches full format info.
-func (c *Client) DetectPlaylist(url string) (bool, *domain.MediaInfo, error) {
-	args := []string{
-		"-J", "--flat-playlist", "--no-download",
-		"--no-warnings",
-		url,
-	}
-	if c.cookiesFile != "" {
-		args = append(args, "--cookies", c.cookiesFile)
-	}
-	if c.proxyURL != "" {
-		args = append(args, "--proxy", c.proxyURL)
-	}
-
-	slog.Info("detecting playlist", "url", url)
-	out, err := c.run(args)
-	if err != nil {
-		return false, nil, fmt.Errorf("yt-dlp playlist detection failed: %w", err)
-	}
-
-	var rawInfo ytdlpInfo
-	if err := json.Unmarshal(out, &rawInfo); err != nil {
-		return false, nil, fmt.Errorf("parse yt-dlp output: %w", err)
-	}
-
-	mi := &domain.MediaInfo{
-		URL:             url,
-		Title:           rawInfo.Title,
-		Uploader:        rawInfo.Uploader,
-		Thumbnail:       rawInfo.Thumbnail,
-		Duration:        rawInfo.Duration,
-		IsPlaylist:      rawInfo.Playlist != "",
-		PlaylistCount:   rawInfo.PlaylistCount,
-		PlaylistEntries: c.parsePlaylistEntries(rawInfo.Entries),
-	}
-
-	return mi.IsPlaylist, mi, nil
-}
-
 func (c *Client) parsePlaylistEntries(entries []json.RawMessage) []domain.PlaylistEntry {
 	var result []domain.PlaylistEntry
 	for _, raw := range entries {