Update MIME type to text/html;profile=mcp-app

Apply MIME type change from commit 0af1532 to all examples and docs.
The profile parameter follows RFC 6838 recommendations for custom
media types, as MCP Apps is a profile of HTML rather than a new syntax.

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

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

docs/quickstart.md

@@ -132,7 +132,9 @@ server.registerResource(resourceUri, resourceUri, {}, async () => {
     "utf-8",
   );
   return {
-    contents: [{ uri: resourceUri, mimeType: "text/html+mcp", text: html }],
+    contents: [
+      { uri: resourceUri, mimeType: "text/html;profile=mcp-app", text: html },
+    ],
   };
 });