🎨 Palette: Add <kbd> tags for keyboard shortcuts

[EiJackGH]

💡 What

Wrapped the keyboard instructions ("Space" and "↑") in semantic <kbd> tags and added corresponding CSS to style them like physical keyboard keys.

🎯 Why

Improves intuitiveness and discoverability for the user. When users see visually styled keys, they immediately recognize them as keyboard controls, which reduces cognitive load compared to parsing plain text instructions.

📸 Before/After

Before: Plain text instruction (Press Space or ↑ to jump!)
After: Visually distinct, physical-looking keys for <kbd>Space</kbd> and <kbd>↑</kbd>.

♿ Accessibility

Using semantic <kbd> tags ensures that browsers and assistive technologies correctly interpret these strings as user keyboard inputs.

Note: Custom CSS was added directly to the existing internal <style> block to match the file's existing architectural pattern without introducing external UI dependencies.

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PR created automatically by Jules for task 14031459458918913234 started by @EiJackGH

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