🎨 Palette: Add explicit empty state for high score

[EiJackGH]

💡 What: Replaced a hidden UI state for new players with an explicit, encouraging empty state message ("None yet. Set a record!").
🎯 Why: Hiding achievement UI elements when the user has no data can leave new users confused about the game's goals. An explicit empty state clarifies the system state, introduces the goal, and improves user onboarding.
📸 Before/After: Before, a first-time player saw no mention of a high score. Now, they see "Personal Best: None yet. Set a record!"
♿ Accessibility: Improves cognitive accessibility by clearly defining the goal and system state for new users, rather than relying on them to discover it organically.

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PR created automatically by Jules for task 2871330578545173002 started by @EiJackGH

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