domain: flip catalog frontend off Jellyfin item-type strings (phase 2a)

Migrate catalog MediaItem consumers from stringly item.type ("Audio",
"MusicAlbum", …) to the neutral item.kind enum across all classification
logic: home, library detail, player routing, artist/person/related/genre
components, tv store.

Model refinements found during migration (each a real distinction the
flat item_type collapsed):
- MediaKind::LiveChannel — live TV (playable, non-seekable) vs
- MediaKind::ChannelItem — channel VOD leaf (playable, seekable) vs
- MediaKind::Channel — channel container (drill-in).
  TvChannel->LiveChannel, non-folder ChannelFolderItem->ChannelItem.

RelatedItemsSection and GenreTags props migrated from Jellyfin type
strings to MediaKind; MediaKind re-exported from api/types.

Deferred by design: display {item.type} text, ResultsCounter labels,
Person.type (role), stream.type (phase 4), and all runTimeTicks/tick math
(coupled to playbackPositionTicks — phase 3). Old fields still dual-carried
so nothing breaks.

Rust 456 + 7 domain tests, frontend 644 tests, check clean.

src/routes/player/[id]/+page.svelte

@@ -5,7 +5,7 @@
   import { convertFileSrc } from "@tauri-apps/api/core";
   import { commands } from "$lib/api/bindings";
   import type { PlayQueueRequest } from "$lib/api/bindings";
-  import type { MediaItem } from "$lib/api/types";
+  import type { MediaItem, MediaKind } from "$lib/api/types";
   import { auth } from "$lib/stores/auth";
   import { library } from "$lib/stores/library";
   import { queue, currentQueueItem, isShuffle, repeatMode, hasNext as hasNextStore, hasPrevious as hasPreviousStore } from "$lib/stores/queue";
@@ -100,7 +100,7 @@
   // Only for audio content - video content uses direct loading and shouldn't be affected by audio queue
   $effect(() => {
     const queueItem = $currentQueueItem;
-    const currentIsVideo = currentMedia?.type === "Movie" || currentMedia?.type === "Episode";
+    const currentIsVideo = currentMedia?.kind === "movie" || currentMedia?.kind === "episode";
     if (queueItem && queueItem.id !== currentMedia?.id && !currentIsVideo) {
       currentMedia = queueItem;
     }
@@ -110,7 +110,8 @@
   // treat it as video when it carries a video media stream.
   function isVideoChannelItem(item: MediaItem): boolean {
     return (
-      item.type === "ChannelFolderItem" &&
+      item.kind === "channelItem" &&
+      // stream.type is Jellyfin stream vocabulary (migrated in a later phase).
       (item.mediaStreams?.some((s) => s.type === "Video") ?? false)
     );
   }
@@ -125,14 +126,13 @@
       console.log("loadAndPlay: Loading item", id);
       // Load item details
       const item = await library.loadItem(id);
-      console.log("loadAndPlay: Loaded item", item.name, "type:", item.type);
+      console.log("loadAndPlay: Loaded item", item.name, "kind:", item.kind);
       currentMedia = item;
 
       // Check if this is a non-playable collection type that should be viewed in library instead
-      const collectionTypes = ["MusicAlbum", "MusicArtist", "Series", "Season", "Folder", "CollectionFolder", "Playlist", "Channel"];
-      // A ChannelFolderItem that is itself a folder is a container, not playable.
-      if (collectionTypes.includes(item.type) || (item.type === "ChannelFolderItem" && item.isFolder)) {
-        console.log("loadAndPlay: Redirecting collection type to library:", item.type);
+      const collectionKinds: MediaKind[] = ["album", "artist", "series", "season", "folder", "playlist", "channel"];
+      if (item.kind && collectionKinds.includes(item.kind)) {
+        console.log("loadAndPlay: Redirecting collection type to library:", item.kind);
         goto(`/library/${id}`);
         return;
       }
@@ -144,8 +144,8 @@
       const alreadyPlayingMedia = get(storeCurrentMedia);
       if (alreadyPlayingMedia?.id === id && !startPosition && !forceRestart) {
         console.log("loadAndPlay: Track already playing, showing UI without restarting");
-        isLive = item.type === "TvChannel";
-        isVideo = item.type === "Movie" || item.type === "Episode" || isLive || isVideoChannelItem(item);
+        isLive = item.kind === "liveChannel";
+        isVideo = item.kind === "movie" || item.kind === "episode" || isLive || isVideoChannelItem(item);
         isPlaying = true;
         loading = false;
         // hasNext/hasPrevious come from the event-driven queue store.
@@ -158,8 +158,8 @@
 
       // Determine if this is video content (Movie, Episode, live TV channels, and
       // channel leaf items that carry a video stream).
-      isLive = item.type === "TvChannel";
-      isVideo = item.type === "Movie" || item.type === "Episode" || isLive || isVideoChannelItem(item);
+      isLive = item.kind === "liveChannel";
+      isVideo = item.kind === "movie" || item.kind === "episode" || isLive || isVideoChannelItem(item);
 
       // When switching to video, stop audio playback and clear the queue
       // This prevents audio from continuing in the background and clears stale state
@@ -330,7 +330,7 @@
             sortOrder: "Ascending",
             limit: 500,
           });
-          const audioTracks = result.items.filter(t => t.type === "Audio");
+          const audioTracks = result.items.filter(t => t.kind === "track");
 
           if (audioTracks.length > 0) {
             // Find the index of the current item in the tracks
@@ -428,7 +428,7 @@
       loading = false;
 
       // Fetch next episode for video episodes (for skip button)
-      console.log("[NextEpisode] Post-load check: isVideo=", isVideo, "currentMedia=", currentMedia?.type, currentMedia?.name);
+      console.log("[NextEpisode] Post-load check: isVideo=", isVideo, "currentMedia=", currentMedia?.kind, currentMedia?.name);
       if (isVideo && currentMedia) {
         fetchNextEpisode(currentMedia);
       } else {
@@ -566,8 +566,8 @@
 
   async function fetchNextEpisode(media: MediaItem) {
     nextEpisode = null;
-    console.log("[NextEpisode] fetchNextEpisode called:", { type: media.type, seriesId: media.seriesId, seasonId: media.seasonId, indexNumber: media.indexNumber, id: media.id, name: media.name });
-    if (media.type !== "Episode" || !media.seasonId || media.indexNumber == null) {
+    console.log("[NextEpisode] fetchNextEpisode called:", { kind: media.kind, seriesId: media.seriesId, seasonId: media.seasonId, indexNumber: media.indexNumber, id: media.id, name: media.name });
+    if (media.kind !== "episode" || !media.seasonId || media.indexNumber == null) {
       console.log("[NextEpisode] Skipping - not an episode or missing seasonId/indexNumber");
       return;
     }
@@ -575,7 +575,7 @@
       const repo = auth.getRepository();
       // Fetch all episodes in the season sorted by episode number
       const result = await repo.getItems(media.seasonId, { sortBy: "IndexNumber", sortOrder: "Ascending", limit: 500 });
-      const episodes = result.items.filter(e => e.type === "Episode");
+      const episodes = result.items.filter(e => e.kind === "episode");
       console.log("[NextEpisode] Season has", episodes.length, "episodes, current index:", media.indexNumber);
 
       // Find the episode after the current one by index number