Function telescopes 

fn telescopes(coupon: &OvernightCoupon) -> bool

Whether the coupon’s projected days can join telescoping runs: every rate accrues over its own span and no bound reads it. A lookback, a cut-off or a daily cap breaks that, and the coupon then takes the day-by-day walk. Both the per-day check and a pass over the strip cost a plain SOFR ladder over 10% of its calibration, so the weights are judged once at build.