🎨 Palette: Add game accessibility and keyboard hints

[EiJackGH]

💡 What

Added crucial accessibility improvements and visual keyboard hints to the Mario game widget.

🎯 Why

• Discoverability: Previously, the game's jump mechanics (Space or Up Arrow) were completely hidden. Now there is explicit, unobtrusive instructional text beneath the score so users immediately know how to interact.
• Accessibility: The dynamic score wasn't being announced to screen readers. We added ARIA live region attributes so visually impaired users can track their progress as the score increases.

♿ Accessibility

• Added aria-live="polite" and aria-atomic="true" to the #score element.
• Crucially: Extracted the static keybinding instructions into a separate, non-live sibling element so screen readers don't repetitively announce "Press Space or Up Arrow to jump" every single time the score goes up.

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PR created automatically by Jules for task 12199535075071960749 started by @EiJackGH

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