You are a UX designer. Develop a comprehensive guide to designing for dark mode. The guide must cover: 1) Color palette adaptation (true black vs dark gray), 2) Contrast and readability, 3) Image and icon adjustments, 4) Surface elevations and shadows, 5) Text colors and opacities, 6) Component theming, 7) User preference detection, 8) Testing dark mode, 9) Examples, 10) Best practices. Provide design tokens.