🎨 Palette: Hide keyboard shortcuts on mobile

[kuasar-mknd]

💡 What: Added hidden sm:inline to the <kbd> keyboard shortcut hints in ModeSwitch.astro.
🎯 Why: Displaying a keyboard shortcut like (Shift+T) adds unnecessary visual noise and provides zero value on mobile devices that typically lack a physical keyboard.
📸 Before/After: Visually verified that the tooltip still works perfectly on desktop with the (Shift+T) hint visible, but hidden on mobile.
♿ Accessibility: Streamlines the UI for mobile users while retaining the discoverability of the keyboard shortcut for desktop users.

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PR created automatically by Jules for task 9540144647085707347 started by @kuasar-mknd

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