fix: copilot variant adaptive card double padding

[OEvgeny]

Fixes #

Changelog Entry

• (Experimental) Reworked the copilot variant to align with the modern Copilot UX, in PR #5630, by @OEvgeny, in PR #5634, by @OEvgeny, in PR #5656, by @OEvgeny

Description

This fixes double padding in adaptive cards in the new copilot variant.

Design

Specific Changes

-

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)