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/lib/trackmap.ts

@@ -0,0 +1,66 @@
+import type { LivePosition, TrackBounds, TrackPoint } from '../types'
+
+export interface CanvasPoint {
+  x: number
+  y: number
+}
+
+const VIEWBOX_SIZE = 100
+
+export function normalizeRawPoint(
+  point: Pick<LivePosition, 'x' | 'y'>,
+  bounds: TrackBounds,
+): CanvasPoint {
+  return {
+    x: normalizeAxis(point.x, bounds.minX, bounds.maxX),
+    y: 1 - normalizeAxis(point.y, bounds.minY, bounds.maxY),
+  }
+}
+
+export function outlinePointToCanvas(point: TrackPoint): CanvasPoint {
+  return {
+    x: clamp01(point.x),
+    y: 1 - clamp01(point.y),
+  }
+}
+
+export function buildOutlinePath(points: ReadonlyArray<TrackPoint>): string {
+  if (points.length < 2) return ''
+
+  return points
+    .map((point, index) => {
+      const canvas = outlinePointToCanvas(point)
+      const command = index === 0 ? 'M' : 'L'
+      return `${command} ${formatSvgCoord(canvas.x)} ${formatSvgCoord(canvas.y)}`
+    })
+    .join(' ')
+}
+
+export function canvasToSvg(point: CanvasPoint): CanvasPoint {
+  return {
+    x: clamp01(point.x) * VIEWBOX_SIZE,
+    y: clamp01(point.y) * VIEWBOX_SIZE,
+  }
+}
+
+export function isOnTrack(status: string | null | undefined): boolean {
+  if (!status) return true
+  const normalized = status.toLowerCase()
+  return normalized === 'ontrack' || normalized === 'on-track' || normalized === 'on_track'
+}
+
+function normalizeAxis(value: number, min: number, max: number): number {
+  const range = max - min
+  if (!Number.isFinite(value) || !Number.isFinite(min) || !Number.isFinite(max)) return 0.5
+  if (range === 0) return 0.5
+  return clamp01((value - min) / range)
+}
+
+function clamp01(value: number): number {
+  if (!Number.isFinite(value)) return 0.5
+  return Math.min(1, Math.max(0, value))
+}
+
+function formatSvgCoord(value: number): string {
+  return (value * VIEWBOX_SIZE).toFixed(2)
+}