Function build_ralph_prompt 

pub fn build_ralph_prompt(
    ito_path: &Path,
    change_repo: &impl DomainChangeRepository,
    module_repo: &impl DomainModuleRepository,
    user_prompt: &str,
    options: BuildPromptOptions,
) -> CoreResult<String>

Build a full Ralph prompt with optional change/module context.

When options.iteration is set, this includes the iteration preamble.