Read live region messages without article and group role words

[Eugene (OEvgeny)]

Screen readers say "article" and "group" before every new message and each of its lines.

Changelog Entry

Fixed

• Fixed screen readers saying "article" and "group" before new messages and each of their lines in the live region, in PR #5921, by @OEvgeny

Description

The live region copy of a message and its attachments were <article>, and each line a <div> or <p> ("group" on Windows), so Narrator read "article, group, Bot WC said:, group, …". Articles are now <div>, and containers and lines inside the message are role="none"; text, aria-atomic, buttons and inputs are unchanged.

Design

• role="none" on lines rather than <p>/<span> (still "group") or one text node (rewrites every renderer); the aria-atomic element itself must stay in the tree.

Specific Changes

• LiveRegionActivity.tsx: <article aria-atomic> → <div aria-atomic>, lines role="none"; props typed with InferReactProps
• LiveRegionAttachments.tsx, LiveRegionSuggestedActions.tsx: wrappers and paragraphs role="none"
• AdaptiveCardAttachment.js, RichCardAttachment.js, core AttachmentForScreenReader/*Attachment.js: <article> → <div>, lines and containers role="none"
• ACCESSIBILITY.md: custom screen reader renderers should do the same
• accessibility/liveRegion/noRoleWords.html: asserts text, aria-atomic, a generic message and only buttons in its accessibility tree

• 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)