Remove temporary JSON-RPC envelope unwrapping hack (#90)

The host implementation has been fixed to return the correct result
format, so this workaround is no longer needed.

Reverts the hack added in #82.

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

Co-authored-by: Claude <noreply@anthropic.com>

src/app.ts

@@ -597,17 +597,11 @@ export class App extends Protocol<Request, Notification, Result> {
     params: CallToolRequest["params"],
     options?: RequestOptions,
   ): Promise<CallToolResult> {
-    const response = await this.request(
+    return await this.request(
       { method: "tools/call", params },
       CallToolResultSchema,
       options,
     );
-    // TEMPORAL HACK: Some host implementations incorrectly return the full
-    // JSON-RPC envelope instead of just the result. Unwrap if needed.
-    if (response && "result" in response && "jsonrpc" in response) {
-      return (response as unknown as { result: CallToolResult }).result;
-    }
-    return response;
   }
 
   /**