🎨 Palette: Add visual jump controls and score accessibility to Mario game

[EiJackGH]

💡 What

Added an on-screen instruction overlay to the Mario mini-game that tells players they can press "Space" or "Up Arrow" to jump.

🎯 Why

Previously, the game only indicated the jump keybindings implicitly in the underlying JavaScript code (keydown event listener for Space and ArrowUp). New users interacting with the widget would not natively know how to play or that the Mario character could jump. Providing visible controls ensures immediate playability and greatly enhances UX.

📸 Before/After

Before: The UI only showed a score text at the top left, Mario, and the ground. No keyboard controls were provided.
After: A semi-transparent overlay "Press Space or Up Arrow to jump" is clearly visible in the top right corner of the game area.

♿ Accessibility

Added aria-live="polite" and aria-atomic="true" to the dynamic div#score tracking element. As Goombas are defeated and the internal score increments, screen readers will now gracefully announce the updated score without aggressively interrupting the user.

Note: Removed the problematic standard library module venv from the requirements.txt as it was breaking the pip setup for local verifications.

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PR created automatically by Jules for task 5765362212074703337 started by @EiJackGH

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