fix(anime): thread episode metadata through stream playback and fix seas

- Split anime browser stream titles into series/season/episode fields (episode-metadata.ts) instead of one joined string, so stats grouping, the mpv title, and the Jimaku/TsukiHime modals all get real values instead of a filename-derived "m3u8"
- Fix AniList season resolver to walk through split-cour sequels and specials without counting them as a season, and to surface rate-limit/network failures instead of falling through to a wrong air-order guess
- Add a Season field to the TsukiHime modal and include later seasons in its search query
- Rewrite WebVTT subtitle tracks as SRT before handing them to alass, since alass has no VTT support and streams serve VTT
- Update CHANGELOG and troubleshooting docs

src/main/runtime/stream-playback-metadata.ts

@@ -0,0 +1,78 @@
+import type { AnimeStreamMetadata } from '../../anime-bridge/episode-metadata';
+import type { AnilistMediaGuess } from '../../core/services/anilist/anilist-updater';
+import type { JimakuMediaInfo } from '../../types';
+
+/**
+ * Holds what the anime browser resolved for the episode currently streaming.
+ *
+ * Consumers otherwise have to re-derive the series and episode from the mpv
+ * title, and some of them only ever see the stream URL, which carries no title
+ * at all. Keeping the resolved fields lets each of them ask instead of guess.
+ */
+export interface StreamPlaybackMetadataStore {
+  set: (metadata: AnimeStreamMetadata) => void;
+  clear: () => void;
+  /**
+   * The metadata for `mediaPath`, or null when the player has moved on to
+   * something else. Matching on the path is what makes this self-expiring —
+   * there is no teardown hook to miss.
+   */
+  match: (mediaPath: string | null) => AnimeStreamMetadata | null;
+}
+
+export function createStreamPlaybackMetadataStore(): StreamPlaybackMetadataStore {
+  let current: AnimeStreamMetadata | null = null;
+
+  return {
+    set(metadata: AnimeStreamMetadata): void {
+      current = metadata;
+    },
+    clear(): void {
+      current = null;
+    },
+    match(mediaPath: string | null): AnimeStreamMetadata | null {
+      if (!current) return null;
+      const trimmed = typeof mediaPath === 'string' ? mediaPath.trim() : '';
+      if (!trimmed) return null;
+      // The stats path is accepted too: stats rewrites the volatile stream URL
+      // to it, so callers reading from there still resolve.
+      return trimmed === current.mediaPath || trimmed === current.statsPath ? current : null;
+    },
+  };
+}
+
+/** AniList counts whole episodes, so a special numbered 6.5 cannot drive it. */
+function wholeEpisode(episode: number | null): number | null {
+  return typeof episode === 'number' && Number.isInteger(episode) && episode > 0 ? episode : null;
+}
+
+/**
+ * The subtitle modals' prefill. `high` confidence is honest here: these fields
+ * came from the source's own listing rather than from a filename guess, so the
+ * modals may search on them without waiting for the user to confirm.
+ */
+export function toJimakuMediaInfo(metadata: AnimeStreamMetadata): JimakuMediaInfo {
+  return {
+    title: metadata.seriesTitle,
+    season: metadata.seasonNumber,
+    episode: wholeEpisode(metadata.episodeNumber),
+    confidence: metadata.episodeNumber !== null ? 'high' : 'low',
+    filename: metadata.displayTitle,
+    rawTitle: metadata.displayTitle,
+  };
+}
+
+/**
+ * The AniList guess, or null when there is no episode to report — in which case
+ * the caller should fall back to parsing the title as usual.
+ */
+export function toAnilistMediaGuess(metadata: AnimeStreamMetadata): AnilistMediaGuess | null {
+  const episode = wholeEpisode(metadata.episodeNumber);
+  if (!metadata.seriesTitle || episode === null) return null;
+  return {
+    title: metadata.seriesTitle,
+    season: metadata.seasonNumber,
+    episode,
+    source: 'stream',
+  };
+}