feat(frontend): add reusable TyreStintTimeline component (#16)

Extract stint timeline SVG from StrategyView into a data-source-agnostic
chart primitive with compound legend, lap-axis ticks, and hover titles.
StrategyView maps race-hub stint data into the new props contract.

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

frontend/src/components/charts/TyreStintTimeline.tsx

@@ -0,0 +1,182 @@
+import { compoundClass } from '../../lib/live'
+import '../../styles/stint-timeline.css'
+
+export interface StintTimelineStint {
+  compound: string
+  lapStart: number
+  lapEnd: number
+  isNew?: boolean
+}
+
+export interface StintTimelineRow {
+  label: string
+  color: string
+  stints: StintTimelineStint[]
+}
+
+interface TyreStintTimelineProps {
+  rows: StintTimelineRow[]
+  totalLaps: number
+}
+
+const SVG_W = 640
+const LEFT = 48
+const RIGHT = 12
+const ROW_H = 28
+const BAR_H = 14
+const BAR_Y = 7
+const AXIS_H = 20
+const BAR_W = SVG_W - LEFT - RIGHT
+
+const COMPOUND_ORDER = ['SOFT', 'MEDIUM', 'HARD', 'INTERMEDIATE', 'WET'] as const
+
+function compoundLabel(compound: string): string {
+  const upper = compound.toUpperCase()
+  if (upper === 'INTERMEDIATE') return 'Intermediate'
+  return upper.charAt(0) + upper.slice(1).toLowerCase()
+}
+
+function stintLength(stint: StintTimelineStint): number {
+  return stint.lapEnd - stint.lapStart + 1
+}
+
+function stintTitle(stint: StintTimelineStint): string {
+  const length = stintLength(stint)
+  return `${compoundLabel(stint.compound)} · L${stint.lapStart}–${stint.lapEnd} · ${length} lap${length === 1 ? '' : 's'}`
+}
+
+function lapX(lap: number, totalLaps: number): number {
+  return LEFT + (lap / totalLaps) * BAR_W
+}
+
+function stintBarX(stint: StintTimelineStint, totalLaps: number): number {
+  return LEFT + ((stint.lapStart - 1) / totalLaps) * BAR_W
+}
+
+function stintBarW(stint: StintTimelineStint, totalLaps: number): number {
+  return Math.max(2, (stintLength(stint) / totalLaps) * BAR_W)
+}
+
+function axisTicks(totalLaps: number): number[] {
+  const ticks: number[] = []
+  for (let lap = 0; lap <= totalLaps; lap += 10) {
+    ticks.push(lap)
+  }
+  return ticks
+}
+
+function collectUsedCompounds(rows: StintTimelineRow[]): string[] {
+  const seen = new Set<string>()
+  for (const row of rows) {
+    for (const stint of row.stints) {
+      seen.add(stint.compound.toUpperCase())
+    }
+  }
+  const ordered = COMPOUND_ORDER.filter((c) => seen.has(c))
+  const extras = [...seen]
+    .filter((c) => !COMPOUND_ORDER.includes(c as (typeof COMPOUND_ORDER)[number]))
+    .sort()
+  return [...ordered, ...extras]
+}
+
+export function TyreStintTimeline({ rows, totalLaps }: TyreStintTimelineProps) {
+  const safeTotal = Math.max(totalLaps, 1)
+  const usedCompounds = collectUsedCompounds(rows)
+  const ticks = axisTicks(safeTotal)
+  const chartH = rows.length * ROW_H
+  const svgH = chartH + AXIS_H + 4
+
+  if (rows.length === 0) {
+    return (
+      <div className="stint-timeline" data-testid="stint-timeline-empty">
+        <div className="stint-timeline__empty">No stint data to display.</div>
+      </div>
+    )
+  }
+
+  return (
+    <div className="stint-timeline" data-testid="stint-timeline">
+      <div className="stint-timeline__scroll">
+        <svg
+          viewBox={`0 0 ${SVG_W} ${svgH}`}
+          className="stint-timeline__svg"
+          role="img"
+          aria-label="Tyre stint timeline"
+        >
+          {rows.map((row, i) => {
+            const rowY = i * ROW_H
+            return (
+              <g key={`${row.label}-${i}`} transform={`translate(0,${rowY})`}>
+                <text
+                  x={LEFT - 5}
+                  y={BAR_Y + BAR_H / 2 + 4}
+                  textAnchor="end"
+                  fill={row.color}
+                  className="stint-timeline__label"
+                >
+                  {row.label}
+                </text>
+
+                {row.stints.map((stint, si) => (
+                  <rect
+                    key={si}
+                    x={stintBarX(stint, safeTotal)}
+                    y={BAR_Y}
+                    width={stintBarW(stint, safeTotal)}
+                    height={BAR_H}
+                    rx={3}
+                    className={`stint-timeline__bar ${compoundClass(stint.compound)}${stint.isNew ? ' stint-timeline__bar--new' : ''}`}
+                  >
+                    <title>{stintTitle(stint)}</title>
+                  </rect>
+                ))}
+              </g>
+            )
+          })}
+
+          <g transform={`translate(0,${chartH})`}>
+            <line
+              x1={LEFT}
+              x2={LEFT + BAR_W}
+              y1={0}
+              y2={0}
+              className="stint-timeline__axis-line"
+            />
+            {ticks.map((lap) => (
+              <g key={lap}>
+                <line
+                  x1={lapX(lap, safeTotal)}
+                  x2={lapX(lap, safeTotal)}
+                  y1={0}
+                  y2={4}
+                  className="stint-timeline__axis-line"
+                />
+                <text
+                  x={lapX(lap, safeTotal)}
+                  y={14}
+                  textAnchor="middle"
+                  className="stint-timeline__axis-tick"
+                >
+                  {lap}
+                </text>
+              </g>
+            ))}
+          </g>
+        </svg>
+      </div>
+
+      <div className="stint-timeline__legend">
+        {usedCompounds.map((compound) => (
+          <span key={compound} className="stint-timeline__legend-item">
+            <span
+              className={`stint-timeline__legend-swatch ${compoundClass(compound)}`}
+              data-testid={`legend-${compound.toLowerCase()}`}
+            />
+            {compoundLabel(compound)}
+          </span>
+        ))}
+        <span className="stint-timeline__meta">{safeTotal} laps</span>
+      </div>
+    </div>
+  )
+}