Podcast episodes play; servers with NodeInfo2 only are described

Castopod announces an episode with a Note that only links to the episode's page, which serves a PodcastEpisode. PrivaPub
reads PodcastEpisode (its words in description, its sound in audio, its cover in image), and a Note that is only a link
to its author's own episode takes the episode's sound, title, cover and words, so the post plays. A server that
publishes no NodeInfo is described from NodeInfo2 (/.well-known/x-nodeinfo2), as Castopod publishes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Federation/Objects/NoteParser.cs

@@ -56,7 +56,7 @@ namespace PrivaPub.Federation.Objects
 
 	public static class NoteParser
 	{
-		static readonly string[] NoteTypes = { "Note", "Article", "Page", "Question", "Event", "Video", "Audio", "Image", "ChatMessage" };
+		static readonly string[] NoteTypes = { "Note", "Article", "Page", "Question", "Event", "Video", "Audio", "Image", "ChatMessage", "PodcastEpisode" };
 		const int MaxAttachments = 16;
 		const int MaxTags = 64;
 
@@ -68,6 +68,8 @@ namespace PrivaPub.Federation.Objects
 			var id = Id(note);
 			if (!NoteTypes.Contains(type) || Origin.Of(id) == default)
 				return default;
+			if (type == "PodcastEpisode")
+				note = Episode(note);
 
 			var (contentHtml, language) = Content(note);
 			var summary = Value(note, "summary");
@@ -123,13 +125,32 @@ namespace PrivaPub.Federation.Objects
 				CoverURL = ObjectShapes.Cover(note),
 				Link = ObjectShapes.Link(note),
 				Video = ObjectShapes.Video(note),
-				Audio = ObjectShapes.Audio(note),
+				Audio = ObjectShapes.Audio(type == "PodcastEpisode" ? note["audio"] as JsonObject : note),
 				Event = ObjectShapes.Event(note),
 				Place = ObjectShapes.NotePlace(note),
 				CommentsEnabled = note["commentsEnabled"] is JsonValue comments && comments.TryGetValue<bool>(out var enabled) ? enabled : null
 			};
 		}
 
+		// Castopod's PodcastEpisode: its words in `description` (a Note of its own), its sound in `audio`, its title the
+		// sound's name; read as a post with those
+		static JsonObject Episode(JsonObject episode)
+		{
+			var note = episode.DeepClone().AsObject();
+			if (note["description"] is JsonObject description)
+			{
+				note["content"] = description["content"]?.DeepClone();
+				note["contentMap"] = description["contentMap"]?.DeepClone();
+				note["mediaType"] = description["mediaType"]?.DeepClone();
+			}
+			if (note["audio"] is JsonObject audio)
+			{
+				note["name"] ??= audio["name"]?.DeepClone();
+				note["attachment"] = new JsonArray(audio.DeepClone());
+			}
+			return note;
+		}
+
 		static (string Html, string Language) Content(JsonObject note)
 		{
 			var content = Value(note, "content");