feat(live): add web track map (#32)

Subscribe to SignalR Position.z and CarData.z, decode DEFLATE payloads, stream throttled positions over SSE, and render live car dots against cached track outline bounds with tap telemetry.

Alignment spike: no checked-in or locally cached real Position.z samples were available in this isolated worktree; verified both streams expose the official raw F1 X/Y/Z coordinate contract and implemented shared-bounds normalization against prefetched OpenF1 outlines. Fallback build-outline-from-stream was not taken.

Playwright remains out of scope for live rendering because BOXBOX_DISABLE_LIVE is used there; coverage is via parser, web handler/SSE, pure transform, and seeded component tests.

frontend/src/test/trackmap.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from 'vitest'
+import {
+  buildOutlinePath,
+  canvasToSvg,
+  isOnTrack,
+  normalizeRawPoint,
+  outlinePointToCanvas,
+} from '../lib/trackmap'
+
+describe('track map transforms', () => {
+  it('normalizes raw F1 coordinates into canvas space', () => {
+    const point = normalizeRawPoint(
+      { x: 50, y: 75 },
+      { minX: 0, maxX: 100, minY: 50, maxY: 100 },
+    )
+    expect(point).toEqual({ x: 0.5, y: 0.5 })
+    expect(canvasToSvg(point)).toEqual({ x: 50, y: 50 })
+  })
+
+  it('centers zero-range bounds and clamps out-of-range points', () => {
+    expect(normalizeRawPoint({ x: 10, y: 20 }, { minX: 10, maxX: 10, minY: 20, maxY: 20 }))
+      .toEqual({ x: 0.5, y: 0.5 })
+    expect(normalizeRawPoint({ x: 20, y: 5 }, { minX: 10, maxX: 15, minY: 10, maxY: 15 }))
+      .toEqual({ x: 1, y: 1 })
+  })
+
+  it('builds an SVG path from normalized outline points', () => {
+    expect(outlinePointToCanvas({ x: 0.25, y: 0.75 })).toEqual({ x: 0.25, y: 0.25 })
+    expect(buildOutlinePath([{ x: 0, y: 0 }, { x: 1, y: 1 }]))
+      .toBe('M 0.00 100.00 L 100.00 0.00')
+    expect(buildOutlinePath([{ x: 0, y: 0 }])).toBe('')
+  })
+
+  it('classifies on-track status defensively', () => {
+    expect(isOnTrack('OnTrack')).toBe(true)
+    expect(isOnTrack('OffTrack')).toBe(false)
+    expect(isOnTrack('')).toBe(true)
+  })
+})