feat: add generated caution text to the messages with corresponding keywords

[OEvgeny]

Fixes #

Changelog Entry

• Added a content generated badge to AI-generated messages, in PR #5298, by @OEvgeny

Description

This PR adds a content generated badge to messages that are identified as AI-generated content.

Design

The implementation targets all white-label and both theme variant experiences:

• In white-label we show a grayed text at the bottom (before references)
• In fluent variant we show a badge before references
• In copilot variant we hide the badge as there is another one on copilot header area

Specific Changes

• Created isAIGeneratedActivity.ts to identify AI-generated content
• Updated TextContent.tsx, MarkdownTextContent.tsx, and PlainTextContent.tsx to include the generated badge
• Modified ActivityDecorator.module.css to style the generated badge
• Updated test files to include scenarios with AI-generated content

-

• 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)