Function build_startup 

pub fn build_startup(
    compiler: &ContextCompiler<'_>,
    budget: &ContextBudget,
    renderer_version: &str,
) -> StartupContext

Build the deterministic startup artifact: the existing System Atlas content (capped at budget.atlas) fused with the budget-selected System Surface Map (the production select_and_render_global pipeline), coverage warnings, and honest omissions. The surface’s omitted ids populate the OMISSIONS section; the ledger records ONLY rendered ids.