🎨 Palette: Add keyboard navigation & modal accessibility to QueueDrawer

[TheDragonSoft]

💡 What: Added focus management, focus restoration on close, Escape key closing via overlayStack, and accessible dialog ARIA attributes (role="dialog", aria-modal, aria-hidden, aria-label) to QueueDrawer.

🎯 Why: Ensures keyboard users and screen reader users can navigate and dismiss the downloads drawer seamlessly without focus getting trapped or lost.

♿ Accessibility: Added role="dialog", aria-modal, aria-hidden, aria-label="Downloads queue", auto-focusing on open, focus restoration to previously focused element on close, and Escape key dismissal through the shared overlayStack.

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PR created automatically by Jules for task 10231868454216168066 started by @TheDragonSoft

[google-labs-jules]

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