T-Bill Ladder Optimizer BETA
Coverage rule: fund Year 1 by splitting the annual need (inflated once) across 3M (3 months),
6M (next 3 months), and 12M (final 6 months). Fund Year 2 (24M) with 12 months × (1+inflation)².
If cash runs out, we stop. Any remainder after coverage goes to the highest-yielding funded rung.
Output will appear here after calculation.