🎨 Palette: Add keyboard shortcut styling to game instructions

[EiJackGH]

💡 What

Wrapped the keyboard instructions ("Space" and "↑") in semantic <kbd> tags and applied CSS styling to render them as physical keys.

🎯 Why

When presenting users with custom keyboard controls, raw text can easily blend into the background or be overlooked. By explicitly styling them as physical keys (with borders and text shadows), it reduces cognitive load and makes the required inputs immediately discoverable and intuitive to use.

📸 Before/After

Before: Text simply read Press Space or ↑ to jump! blending in with standard paragraph styling.
After: The keys Space and ↑ are distinctly styled as keyboard buttons with a light background and drop shadows to stand out against the dynamic game background.

♿ Accessibility

Improves accessibility by explicitly communicating interactivity through distinct, recognizable physical affordances. The use of the semantic <kbd> element correctly denotes keyboard input for assistive technologies.

---

PR created automatically by Jules for task 6296474647881729026 started by @EiJackGH

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.