feat(music): add --model flag to music cover command

- Users can now override model with --model (music-cover or music-cover-free)
- Default still uses musicCoverModel() → music-cover (sk-cp) / music-cover-free (free tier)

Author: Raylan LIN

src/commands/music/cover.ts

@@ -13,9 +13,10 @@ import { musicCoverModel } from './models';
 
 export default defineCommand({
   name: 'music cover',
-  description: 'Generate a cover version of a song based on reference audio (music-cover-free)',
+  description: 'Generate a cover version of a song based on reference audio (music-cover / music-cover-free)',
   usage: 'mmx music cover --prompt <text> (--audio <url> | --audio-file <path>) [--lyrics <text>] [--out <path>] [flags]',
   options: [
+    { flag: '--model <model>', description: 'Model: music-cover (Token Plan), music-cover-free (Pay-as-you-go, default). Override only if needed.' },
     { flag: '--prompt <text>', description: 'Target cover style, e.g. "Indie folk, acoustic guitar, warm male vocal"' },
     { flag: '--audio <url>', description: 'URL of the reference audio (mp3, wav, flac, etc. — 6s to 6min, max 50MB)' },
     { flag: '--audio-file <path>', description: 'Local reference audio file (auto base64-encoded)' },
@@ -66,7 +67,7 @@ export default defineCommand({
     const outPath = (flags.out as string | undefined) ?? `cover_${ts}.${ext}`;
     const format = detectOutputFormat(config.output);
 
-    const model = musicCoverModel(config);
+    const model = (flags.model as string) || musicCoverModel(config);
     const body: MusicRequest = {
       model,
       prompt,