Add sheet-music-server example

Demo MCP App showcasing ABC notation rendering and audio playback with:
- Server-side ABC notation validation
- Built-in audio player with play/pause and loop controls
- Sheet music visualization using abcjs library

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

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

examples/sheet-music-server/src/global.css

@@ -0,0 +1,12 @@
+* {
+  box-sizing: border-box;
+}
+
+html, body {
+  font-family: system-ui, -apple-system, sans-serif;
+  font-size: 1rem;
+}
+
+code {
+  font-size: 1em;
+}