Function prepare_architect_task_plan 

pub fn prepare_architect_task_plan(
    output_root: &Path,
    task: &ArchitectQueuedTask,
    synthesis: &AppModelSynthesis,
    backend: &DbBackendConfig,
    operations: &dyn DatabaseOperations,
) -> Result<ArchitectPreparedPlan, AgentErrorKind>

Prepares one Architect review workspace, source scaffold, bounded change plan, and review summary.