Lazy-import OpenAIAgentsPlugin to fix opentelemetry.sdk import error

The top-level import of OpenAIAgentsPlugin in temporal/utils.py triggers
the temporalio.contrib.opentelemetry chain which requires opentelemetry-sdk.
This breaks all agents (including sync ones) when opentelemetry-sdk is not
installed. Moving the import to the only function that uses it
(get_temporal_client) avoids this for non-Temporal agents.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: danielmillerp

src/agentex/lib/core/clients/temporal/utils.py

@@ -6,7 +6,6 @@
 from temporalio.worker import Interceptor
 from temporalio.runtime import Runtime, TelemetryConfig, OpenTelemetryConfig
 from temporalio.contrib.pydantic import pydantic_data_converter
-from temporalio.contrib.openai_agents import OpenAIAgentsPlugin
 
 # class DateTimeJSONEncoder(AdvancedJSONEncoder):
 #     def default(self, o: Any) -> Any:
@@ -97,6 +96,8 @@ async def get_temporal_client(temporal_address: str, metrics_url: str | None = N
         validate_client_plugins(plugins)
 
     # Check if OpenAI plugin is present - it needs to configure its own data converter
+    # Lazy import to avoid pulling in opentelemetry.sdk for non-Temporal agents
+    from temporalio.contrib.openai_agents import OpenAIAgentsPlugin
     has_openai_plugin = any(
         isinstance(p, OpenAIAgentsPlugin) for p in (plugins or [])
     )