Add progress bar and seek controls to Motif player

- Add interactive progress bar with visual fill indicator
- Show current time and total duration
- Enable seeking/scrubbing through the synthesis
- Improve Motif player UX with cleaner layout
- Add progress tracking that updates 10x per second
- Format time display as MM:SS
- Progress bar appears when playback starts
- Seeking updates event indices for smooth playback

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/core/MotifEngine.ts

@@ -134,6 +134,33 @@ export class MotifEngine {
     }
   }
 
+  seek(progress: number): void {
+    if (this.synthesisEngine) {
+      this.synthesisEngine.seek(progress);
+    }
+  }
+
+  getProgress(): number {
+    if (this.synthesisEngine) {
+      return this.synthesisEngine.getProgress();
+    }
+    return 0;
+  }
+
+  getCurrentTime(): number {
+    if (this.synthesisEngine) {
+      return this.synthesisEngine.getCurrentTime();
+    }
+    return 0;
+  }
+
+  getDuration(): number {
+    if (this.synthesisEngine) {
+      return this.synthesisEngine.getDuration();
+    }
+    return 0;
+  }
+
   private generateSyntheticMIDI(songName: string): NoteEvent[] {
     // Generate procedural MIDI based on song name hash
     const hash = this.simpleHash(songName);