Function render_ablation_surface 

pub fn render_ablation_surface(
    root: &Path,
    mode: SurfaceAblation,
    goal: &str,
    budget_tokens: usize,
) -> Result<String, String>

Render one ablation-mode task surface for goal under budget_tokens (the chars/4 estimate) through the PRODUCTION surface pipeline (build_surface_staged) with the mode’s stage toggle — the ablation rows are the production rows with one stage removed, never a harness reimplementation of ranking. A one-line mode label prefixes the production render so artifacts stay identifiable; the label’s token cost is subtracted from the budget (equal-token discipline: the final artifact never exceeds the cap).