feat: resolve trial-only playback via trialDuration/effectiveDuration

VIP songs for non-VIP accounts return a ~30s trial fragment. The player used the full duration for isNearEnd, so the trial end didn't trigger auto-advance (~60s stall), and currentSong.duration stayed full, leaving the UI progress stuck.

- provider.ts: SongUrlResult {url, trialDuration?}; getSongUrl signature
- netease.ts: parseNeteaseTrial (freeTrialInfo start/end in seconds) + getSongUrl
- qq.ts: parseQqTrial (isTryout/tryEnd) + getSongUrl
- bilibili/youtube: getSongUrl returns {url}
- instance.ts: resolveAndPlay uses effectiveDuration = trialDuration ?? duration -> nearEnd at trial end -> native auto-advance; BotStatus.effectiveDuration
- VIP account: freeTrialInfo absent -> full duration -> full playback (no toggle)

Backward compatible (optional fields; getSongUrl has a single caller, updated).
Tests: parseTrial assertions (seconds/alias/ms-fallback). 14 pass.

src/music/youtube.ts

@@ -7,6 +7,7 @@ import type {
   MusicProvider,
   Song,
   SongWithUrl,
+  SongUrlResult,
   Playlist,
   Album,
   SearchResult,
@@ -134,7 +135,7 @@ export class YouTubeProvider implements MusicProvider {
     }
   }
 
-  async getSongUrl(songId: string): Promise<string | null> {
+  async getSongUrl(songId: string): Promise<SongUrlResult | null> {
     try {
       const url = `https://www.youtube.com/watch?v=${songId}`;
       const raw = await runYtDlp([
@@ -146,7 +147,7 @@ export class YouTubeProvider implements MusicProvider {
         "--quiet",
       ], 45_000);
       const audioUrl = raw.trim().split("\n")[0];
-      return audioUrl || null;
+      return audioUrl ? { url: audioUrl } : null;
     } catch {
       return null;
     }