🎨 Palette: Improve accessibility of anchor buttons for modals

[0m364]

💡 What: Added role="button" and aria-haspopup="dialog" to native <a> tags used as buttons, and explicitly bound the Spacebar key to the action to prevent page scrolling.
🎯 Why: Native <a> tags only respond to Enter. Screen reader and keyboard users expect elements functioning as buttons to also trigger on Spacebar. Defaulting to scroll creates a confusing experience.
📸 Before/After: Visuals remain unchanged, but the element now correctly responds to Spacebar without scrolling.
♿ Accessibility: Ensures correct ARIA semantic roles and restores standard keyboard expectations for interactive elements.

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PR created automatically by Jules for task 429815404078661445 started by @0m364

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