🎨 Palette: Improve countdown feedback and high-score visibility

[aidasofialily-cmd]

I've implemented several micro-UX improvements to the SPEED CLICKER game to make it more engaging and rewarding, especially for new players.

Key improvements:

• Visual Polish: The countdown digits (3, 2, 1) are now highlighted in yellow, and the "GO!" prompt is green, creating a clearer transition from the menu to gameplay.
• Immediate Feedback: New players now see the "NEW BEST! 🥳" indicator as soon as they score their first point, providing immediate positive reinforcement that was previously hidden for first sessions.
• Persistent Goal Visibility: The session's high score is now displayed in real-time next to the current score, so players always know how close they are to beating their record.
• Inclusive Congratulations: First-time players now receive the final "Congratulations! A new personal best!" message, ensuring a delightful first-run experience.

These changes were implemented in src/main.cpp and verified using non-interactive terminal tests. Accessibility and core UX (like cursor hiding) were preserved.

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PR created automatically by Jules for task 10165045485918488442 started by @aidasofialily-cmd

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