- Introduced logic to trigger a follow-up turn when the manual opener greeting is empty.
- Updated `_execute_manual_opener_tool_calls` to return structured tool call and result data.
- Added `_build_manual_opener_follow_up_context` method to construct context for follow-up turns.
- Modified `_handle_turn` to accept system context for improved conversation management.
- Enhanced tests to validate the new follow-up behavior and ensure proper context handling.