Announce status flashes to screen readers with aria-live

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What is this about?

Problem

Status messages ("Capture a screen first", "Couldn't save that", etc.) update visually but aren't announced to assistive tech.

Where to look

• index.html — #status element (~613)
• index.html — flash() function (~1121)

Acceptance criteria

• Status region uses aria-live (polite for info, assertive for errors if appropriate)
• Busy/success/error messages are announced
• Idle/default status doesn't spam announcements

Skills needed

One HTML attribute + small JS tweak.