feat(frontend): annotate key numbers with meaning (#18)

Add shared Meaning primitive and pure interpretation helpers for interval,
tyre age, and championship gap columns on the live tower, tyre deg panel,
and championship hub. Thresholds are exported consts (undercut window tied
to PIT_LOSS_SECONDS from #13).

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/test/LiveComponents.test.tsx

@@ -189,6 +189,26 @@ describe('TimingTower', () => {
     expect(screen.getByText(/no driver timing rows/i)).toBeInTheDocument()
   })
 
+  it('annotates DRS-range intervals in race mode', () => {
+    const raceRows = [
+      makeRow('1', 1, 'VER'),
+      makeRow('4', 2, 'NOR', { Interval: '+0.4', GapToLeader: '+0.4' }),
+    ]
+    render(
+      <TimingTower
+        rows={raceRows}
+        session={{
+          MeetingName: 'Monaco Grand Prix',
+          CircuitName: 'Monaco',
+          SessionType: 'Race',
+          SessionName: 'Race',
+          Path: '',
+        }}
+      />,
+    )
+    expect(screen.getByText('DRS range')).toBeInTheDocument()
+  })
+
   it('renders the SQ1 cutoff after P17 and marks rows below as at risk', () => {
     const sprintRows = Array.from({ length: 22 }, (_, index) =>
       makeRow(String(index + 1), index + 1, `D${index + 1}`),