feat(explain): display formatting kernel + card/layout redesign

User acceptance feedback round:
- format.ts: magnitude-aware measure formatting, bin-width-aware range
  labels (fixes raw float precision leaking into descriptions/axes,
  e.g. '11.399379999999999,17.099069999999998' -> '11.4-17.1')
- explainers route all description params and chart titles through it
- UI (Codex): overview filter chips with counts, title-first cards
  (strength pill + 'field -> measure'), 340px chart/detail split,
  strength-then-score sorting, sectioned counts, collapsed skip footer

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>