Share race & session results

[burkben]

What & why

Phase 5 "share results." Race nights are social — this lets you fling a clean recap to Messages / Notes / AirDrop straight from the app. A Share button now lives on:

• the finished-race view (race.tsx) — a celebratory recap with splits + lap-by-lap, and
• a History session detail (history/[id].tsx) — a session summary with the fastest passes.

Both hand plain text to the OS share sheet via React Native's built-in Share API — no new native module, so nothing to miss in a dev build (unlike the ExpoSQLite gotcha).

How

• New pure module apps/mobile/src/share/summary.ts (+13 tests):
  • raceShareText(result, { carName }) — 🏁 player finished N laps in T, best/avg/worst splits, and a numbered lap list with the fastest lap flagged ⚡.
  • sessionShareText(session, passes, { display, carNames, topN }) — date, pass count, duration, best, and the top-N fastest passes.
  • formatLapTime mirrors race.tsx's on-screen clock; speeds run through the same speed/format converter as every readout, so a shared number honors the user's unit + calibration exactly.
• race.tsx — "Share result" button resolves the car's garage nickname, honors the haptics setting.
• history/[id].tsx — header "Share" action (shown once a session has passes), passing the live speed display + a car-nickname map.

Example race share:

🏁 Ben finished 3 laps in 7.40s
Car: Twin Mill

Best lap 2.10s (lap 2)
Average 2.47s
Worst lap 2.80s (lap 3)

Laps:
  1. 2.50s
  2. 2.10s ⚡
  3. 2.80s

via RedlineID

Tests / gates

• 178 vitest pass (+13 share). tsc --noEmit clean · expo export --platform ios clean.

Notes

• Pure logic is fully covered; the share sheet itself is a thin Share.share({ message }) call (no device needed to compile/typecheck) — safe to land unverified and try on-device whenever.
• Also refreshed stale ROADMAP Phase 5 checkboxes (Achievements → Achievements engine — unlockable badges (Racing · Speed · Collection) #23, speed units → Speed units (mph/km/h) + display calibration #25, this → Share race & session results #26) and split the old "Multiplayer; share results" bullet so only the shipped half is ticked.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>