Upgrade live timing page for race weekends

- Track status flag banner (green/yellow/SC/VSC/red, defensive mapping)
- Weather strip: air/track temp, humidity, wind with compass, rain badge
- Gap trend sparklines from a per-driver interval ring buffer
- Battle detection: consecutive cars within 1.0s chained and highlighted
- Stint history column with compound sequence per driver
- Pinnable drivers (max 3) with focus cards, persisted to localStorage

Pure logic lives in lib/gapHistory.ts and lib/battles.ts with unit
tests; 137 frontend tests passing.

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

frontend/src/components/live/TrackStatusBanner.tsx

@@ -0,0 +1,17 @@
+import { trackStatusInfo } from '../../lib/live'
+
+interface Props {
+  status: string | null | undefined
+}
+
+export function TrackStatusBanner({ status }: Props) {
+  if (!status) return null
+  const info = trackStatusInfo(status)
+
+  return (
+    <div className={`track-banner track-banner-${info.key}`} role="status" data-testid="track-banner">
+      <span className="track-banner-label">{info.label}</span>
+      {info.detail && <span className="track-banner-detail">{info.detail}</span>}
+    </div>
+  )
+}