Validate that Cursor is capable of authenticating with ToolHive

[yrobla]

[yrobla]

Same issue as vscode:

Client error for command HTTP 403: Invalid OAuth error response: [
  {
    "code": "invalid_type",
    "expected": "string",
    "received": "undefined",
    "path": [
      "error"
    ],
    "message": "Required"
  }
]. Raw body: {"errorCode":"E0000005","errorSummary":"Invalid session","errorLink":"E0000005","errorId":"oaePqaddTBnRKexrtilGXZ_BA","errorCauses":[]}