Ported onto current main after the locale-grouping change in overview.ts;
review follow-ups included:
- explicit note: budgets count the full would-be API cost including
subscription-proxied spend, consistent with the overview Cost total
- percent display floors the raw value on both surfaces, so 99.6 percent
renders as 99 percent in warn state and 100 percent appears only when the
state is over; regression tests cover the boundary on overview and --check
- overview keeps main's en-US locale-grouped formatting and the
unpriced-model warning block; the budget line renders after it
