🎨 Palette: Add ARIA labels to icon-only action buttons

[thirdeyenation]

💡 What: Added aria-label attributes to icon-only action buttons in the message queue and tasks list components, and hid the material icon text from screen readers using aria-hidden="true".
🎯 Why: To ensure screen reader users can identify the purpose of these icon-only buttons, as without labels they just read as raw icon text (e.g., "keyboard double arrow right").
📸 Before/After: N/A - visual appearance is unchanged, strictly DOM accessibility improvements.
♿ Accessibility: Improves accessibility significantly for keyboard navigation and screen reader users by properly narrating button functions instead of ligatures.

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PR created automatically by Jules for task 16896623566007109092 started by @thirdeyenation

[google-labs-jules]

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