🎨 Palette: Improve accessibility and instructions for Mario Game

[EiJackGH]

💡 What

• Added explicit, visible instructional text (Press Space or Up Arrow to jump) to the Mario game UI.
• Styled the instructions so they don't interfere with gameplay (pointer-events: none).
• Added aria-live="polite" and aria-atomic="true" to the dynamic score counter.
• Removed invalid built-in venv module from requirements.txt to unblock local testing.

🎯 Why

• Users do not intuitively know which keys trigger custom game events without instructions.
• Screen readers previously did not announce score updates when the counter incremented, rendering the game state inaccessible for those users.
• venv was breaking pip install -r requirements.txt, preventing local verification.

♿ Accessibility

• Score updates are now broadcasted properly via screen reader aria-live regions.
• Keybindings are explicitly listed, improving cognitive accessibility.

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PR created automatically by Jules for task 3372022207802537599 started by @EiJackGH

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