fix: use direct agent api per request

sdk/upstream_agent_api.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+_api_root = Path(__file__).resolve().parents[1] / "external" / "platform-agent_api"
+if str(_api_root) not in sys.path:
+    sys.path.insert(0, str(_api_root))
+
+from lambda_agent_api.agent_api import AgentApi, AgentBusyException, AgentException  # noqa: E402
+from lambda_agent_api.server import MsgEventSendFile, MsgEventTextChunk  # noqa: E402
+
+__all__ = [
+    "AgentApi",
+    "AgentBusyException",
+    "AgentException",
+    "MsgEventSendFile",
+    "MsgEventTextChunk",
+]