Part of #57 — Task 4: Tutorial & Onboarding
- 5 click-through screens introducing game concepts (code, buildings,
research, phases, keyboard shortcuts)
- Skip button on every screen, keyboard support (Enter/Escape/arrows)
- Stores completion in localStorage — only shows once for new players
- Matches existing visual style (dark theme, accent colors, monospace)
- Start Playing button on final screen with shortcut hint (? overlay)
