feat: add optional output_dir param to extract_thumbnails

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/bindings/mediaAnalysis.ts

@@ -41,11 +41,13 @@ export async function extractWaveformTiers(
 
 export async function extractThumbnails(
   filePath: string,
-  duration: number
+  duration: number,
+  outputDir?: string
 ): Promise<ThumbnailSpritesheet[]> {
   return invoke<ThumbnailSpritesheet[]>('extract_thumbnails', {
     filePath,
     duration,
+    outputDir: outputDir ?? null,
   });
 }