fix: add missing call_type to stream adapter ProviderTrace (#9259)

Both letta_llm_stream_adapter and simple_llm_stream_adapter were
creating ProviderTrace without call_type, causing "unknown" in
ClickHouse analytics.

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Co-authored-by: Letta <noreply@letta.com>

letta/adapters/simple_llm_stream_adapter.py

@@ -254,6 +254,7 @@ class SimpleLLMStreamAdapter(LettaLLMStreamAdapter):
                         agent_id=self.agent_id,
                         agent_tags=self.agent_tags,
                         run_id=self.run_id,
+                        call_type="agent_step",
                         org_id=self.org_id,
                         user_id=self.user_id,
                         llm_config=self.llm_config.model_dump() if self.llm_config else None,