fix(panel): keep question prompts inside the card padding

[zzalancelot]

Summary

• The confirmation card rendered its prompt inside a fieldset legend, so the browser painted that text on the border and ignored the card padding.
• The prompt now stays in normal flow, lined up with the options, and option radios are vertically centered.

Test plan

• Preview the question card: prompt sits inside the gray panel padding and shares the options' left edge
• Radio is vertically centered in a two-line option
• Reload the extension and confirm a live ask_user card no longer clips the title against the top edge

Confidence Score: 5/5

The PR appears safe to merge with no outstanding findings.

Summary

Keeps question prompts within the card’s padded content area while preserving the fieldset’s complete accessible name.

• Moves the visible prompt into normal document flow and hides the duplicated visual content from assistive technology.
• Builds the hidden legend from the question index, header, question, and detail.
• Adjusts card and option spacing and vertically centers radio controls.

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