toolResponses function
Tool results to send back to Gemini: chat.sendMessage(toolResponses(r)).
Use this instead of firebase_ai's Content.functionResponses, which uses
the role function: newer Gemini models reject it with "Role 'function'
is not supported". This uses the role user, which Gemini accepts.
Implementation
Content toolResponses(Iterable<FunctionResponse> responses) =>
Content('user', responses.toList());