Add sheet-music-server example

[jonathanhefner]

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

Screenshots:

Twinkle, Twinkle	Playing on repeat

(Will push those screenshots to the gh-pages branch once this PR is merged.)

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/ext-apps/@modelcontextprotocol/ext-apps@196

commit: 012fb32

[antonpk1]

very cool! one thing - the audio playback doesn't work because the soundfonts from paulrosen.github.io are blocked by CSP.

fix: add connectDomains to the resource response in server.ts:

return {
  contents: [
    {
      uri: resourceUri,
      mimeType: RESOURCE_MIME_TYPE,
      text: html,
      _meta: {
        ui: {
          csp: {
            // Allow loading soundfonts from paulrosen.github.io for audio playback
            connectDomains: ["https://paulrosen.github.io"],
          },
        },
      },
    },
  ],
};

[jonathanhefner]

@antonpk1 Thank you!! I applied your fix.