TokenUsageMeter

<section class="tum-card" aria-labelledby="tumTitle">
  <header class="tum-head">
    <h2 id="tumTitle" class="tum-title">Token budget</h2>
    <span class="tum-meta" id="tumMeta">5,120 / 8,000</span>
  </header>
  <div class="tum-track" role="meter" aria-valuemin="0" aria-valuemax="8000" aria-valuenow="5120" aria-labelledby="tumTitle tumMeta">
    <div class="tum-fill" id="tumFill"></div>
  </div>
  <p class="tum-hint" id="tumHint">64% used — safe for one more long response.</p>
</section>