API 服务 Create the FastAPI application. Bases: BaseModel Schema for streaming chat requests. Bases: BaseModel Incoming WebSocket payload. Bases: BaseModel Outgoing WebSocket envelope. Bases: BaseModel Serialized MCP server response model. Bases: BaseModel Serialized MCP credential response model. Bases: BaseModel Serialized agent MCP mount response model. Bases: BaseModel Serialized MCP call audit response model.