refactor: lazy-import LLM client modules in factory to avoid SDK init at collection time

tradingagents/llm_clients/factory.py

@@ -1,10 +1,6 @@
 from typing import Optional
 
 from .base_client import BaseLLMClient
-from .openai_client import OpenAIClient
-from .anthropic_client import AnthropicClient
-from .google_client import GoogleClient
-from .azure_client import AzureOpenAIClient
 
 # Providers that use the OpenAI-compatible chat completions API
 _OPENAI_COMPATIBLE = (
@@ -20,6 +16,9 @@ def create_llm_client(
 ) -> BaseLLMClient:
     """Create an LLM client for the specified provider.
 
+    Client modules are imported lazily so that collecting tests or importing
+    the package does not trigger heavy LLM SDK initialization.
+
     Args:
         provider: LLM provider name
         model: Model name/identifier
@@ -35,15 +34,19 @@ def create_llm_client(
     provider_lower = provider.lower()
 
     if provider_lower in _OPENAI_COMPATIBLE:
+        from .openai_client import OpenAIClient
         return OpenAIClient(model, base_url, provider=provider_lower, **kwargs)
 
     if provider_lower == "anthropic":
+        from .anthropic_client import AnthropicClient
         return AnthropicClient(model, base_url, **kwargs)
 
     if provider_lower == "google":
+        from .google_client import GoogleClient
         return GoogleClient(model, base_url, **kwargs)
 
     if provider_lower == "azure":
+        from .azure_client import AzureOpenAIClient
         return AzureOpenAIClient(model, base_url, **kwargs)
 
     raise ValueError(f"Unsupported LLM provider: {provider}")