Add one-line score visualizer with 3D orb and MP4 export

- Verovio single-system engraving, MuseScore audio/MIDI from the same source
- React + Remotion player with live camera, colour and orb controls
- Express pipeline, render queue and local H.264/AAC export
- MIT license plus third-party notices for the reference skill

index.html

@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="zh-CN">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta name="color-scheme" content="dark" />
+    <title>Music Visualizer · 单行乐谱</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/client/main.tsx"></script>
+  </body>
+</html>