Formats the system prompt by combining base prompt with custom instructions.
A 'custom' expertise selection is mapped to 'advanced' upstream (see
ChatService.getLlmResponse), so the base prompt is always one of the three
levels above with the custom instruction appended.
Formats the system prompt by combining base prompt with custom instructions. A 'custom' expertise selection is mapped to 'advanced' upstream (see ChatService.getLlmResponse), so the base prompt is always one of the three levels above with the custom instruction appended.