createAnthropicChatProvider function
Create an Anthropic provider for chat
Implementation
AnthropicProvider createAnthropicChatProvider({
  required String apiKey,
  String model = 'claude-sonnet-4-20250514',
  String? systemPrompt,
  double? temperature,
  int? maxTokens,
}) {
  return createAnthropicProvider(
    apiKey: apiKey,
    model: model,
    systemPrompt: systemPrompt,
    temperature: temperature,
    maxTokens: maxTokens,
  );
}