- Added support for "developer" role messages in conversation context across all LLM adapters. For non-OpenAI services (Anthropic, Google, AWS Bedrock), an initial "developer" message is promoted to the system instruction when no `system_instruction` is configured; otherwise it is converted to a "user" message. For OpenAI services, "developer" messages pass through in conversation history. For the Responses API, they are kept as "developer" role (matching the existing "system" → "developer" conversion).
