🎨 Palette: Add explicit jump instructions to Mario game

[EiJackGH]

💡 What:
Added visible jump instructions ("Press Space or Up Arrow to jump!") to the Mario game UI. Also added aria-live="polite" and aria-atomic="true" to the score counter.

🎯 Why:
For custom web games, users often don't know the required keybindings, leading to frustration. Explicit instructions solve this. Making the score readable to screen readers improves overall accessibility.

📸 Before/After:
Before: The screen showed the game and score, but no hints on how to play.
After: A faint instructions overlay sits right below the score to help the user.

♿ Accessibility:

• Added aria-live regions to the dynamic score div so that screen readers announce changes.

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PR created automatically by Jules for task 16359104647986240653 started by @EiJackGH

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