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/test/battles.test.ts

@@ -0,0 +1,118 @@
+import { describe, expect, it } from 'vitest'
+import { battleLabel, battleNumbers, detectBattles, isRaceSession } from '../lib/battles'
+import type { LiveTimingRow } from '../lib/live'
+import type { LiveDriverData } from '../types'
+
+function row(
+  number: string,
+  position: number,
+  interval: string,
+  tla: string,
+  overrides: Partial<LiveDriverData> = {},
+): LiveTimingRow {
+  return {
+    RacingNumber: number,
+    Position: position,
+    Driver: {
+      RacingNumber: number,
+      Position: position,
+      Interval: interval,
+      GapToLeader: interval,
+      InPit: false,
+      PitOut: false,
+      Retired: false,
+      ...overrides,
+    } as LiveDriverData,
+    Info: {
+      RacingNumber: number,
+      BroadcastName: '',
+      Tla: tla,
+      TeamName: '',
+      TeamColour: '',
+      FirstName: '',
+      LastName: '',
+    },
+  }
+}
+
+describe('isRaceSession', () => {
+  it('only treats race and sprint sessions as races', () => {
+    expect(isRaceSession('Race')).toBe(true)
+    expect(isRaceSession('Sprint')).toBe(true)
+    expect(isRaceSession('Qualifying')).toBe(false)
+    expect(isRaceSession('Practice')).toBe(false)
+    expect(isRaceSession('')).toBe(false)
+    expect(isRaceSession(undefined)).toBe(false)
+  })
+})
+
+describe('detectBattles', () => {
+  const rows = [
+    row('1', 1, '', 'VER'),
+    row('4', 2, '+0.4', 'NOR'),
+    row('81', 3, '+0.8', 'PIA'),
+    row('16', 4, '+5.0', 'LEC'),
+    row('44', 5, '+0.9', 'HAM'),
+    row('63', 6, '+12.2', 'RUS'),
+  ]
+
+  it('groups consecutive cars within 1.0s in race sessions', () => {
+    const battles = detectBattles(rows, 'Race')
+    expect(battles).toHaveLength(2)
+    expect(battles[0].drivers.map((d) => d.code)).toEqual(['VER', 'NOR', 'PIA'])
+    expect(battles[0].minGap).toBeCloseTo(0.4)
+    expect(battles[1].drivers.map((d) => d.code)).toEqual(['LEC', 'HAM'])
+    expect(battles[1].minGap).toBeCloseTo(0.9)
+  })
+
+  it('returns nothing outside race sessions', () => {
+    expect(detectBattles(rows, 'Qualifying')).toEqual([])
+    expect(detectBattles(rows, undefined)).toEqual([])
+  })
+
+  it('excludes cars in the pits or retired', () => {
+    const pitted = [
+      row('1', 1, '', 'VER'),
+      row('4', 2, '+0.4', 'NOR', { InPit: true }),
+      row('81', 3, '+0.6', 'PIA'),
+      row('16', 4, '+8.0', 'LEC'),
+      row('44', 5, '+0.5', 'HAM', { Retired: true }),
+    ]
+    const battles = detectBattles(pitted, 'Race')
+    expect(battles).toEqual([])
+  })
+
+  it('ignores lapped and missing intervals', () => {
+    const lapped = [
+      row('1', 1, '', 'VER'),
+      row('4', 2, '1L', 'NOR'),
+      row('81', 3, '', 'PIA'),
+    ]
+    expect(detectBattles(lapped, 'Race')).toEqual([])
+  })
+
+  it('handles empty and single-row input', () => {
+    expect(detectBattles([], 'Race')).toEqual([])
+    expect(detectBattles([row('1', 1, '', 'VER')], 'Race')).toEqual([])
+  })
+})
+
+describe('battleLabel / battleNumbers', () => {
+  it('formats a two-car chip label', () => {
+    const battles = detectBattles([row('1', 1, '', 'VER'), row('4', 2, '+0.4', 'NOR')], 'Race')
+    expect(battleLabel(battles[0])).toBe('VER ⚔ NOR +0.4')
+  })
+
+  it('collects racing numbers across all battles', () => {
+    const battles = detectBattles(
+      [
+        row('1', 1, '', 'VER'),
+        row('4', 2, '+0.4', 'NOR'),
+        row('16', 3, '+9.0', 'LEC'),
+        row('44', 4, '+0.7', 'HAM'),
+      ],
+      'Race',
+    )
+    expect(battleNumbers(battles)).toEqual(new Set(['1', '4', '16', '44']))
+  })
+})