🎨 Palette: Improve Mario game accessibility and instructional UX

[EiJackGH]

💡 What:
Added visual instructions ("Press Space or Up Arrow to jump") to the Mario game UI. Separated the static "Score:" label from the dynamic value and wrapped the value in an aria-live region.

🎯 Why:
Users playing the game for the first time did not inherently know which keys controlled Mario, leading to confusion. Additionally, the previous score setup forced screen readers to announce "Score: 1", "Score: 2" entirely instead of just the new number, causing unnecessary cognitive load and repetitive announcements.

📸 Before/After:
(Visual changes verified via local Playwright screenshot)
Before: Only "Score: X" in the top-left corner.
After: "Score: X" with a subtle "Press Space or Up Arrow to jump" instruction underneath.

♿ Accessibility:

• Added aria-live="polite" and aria-atomic="true" specifically to the score value <span> so screen readers only announce the dynamic number change, rather than repeating the static "Score: " text every single point.

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PR created automatically by Jules for task 16197173697268521598 started by @EiJackGH

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