[Eugene (OEvgeny)]

Continues the CSS Modules migration (#5997).

Changelog Entry

Changed

• Converted the chat history box, image avatar, error box, transcript list and media attachments to CSS Modules with webchat__ class names, and videoHeight to --webchat__height--video, in PR #6024, by @OEvgeny

Removed

• 💥 Deprecated the activities, audioAttachment, audioContent, chatHistoryBox, errorBox, imageAvatar, videoAttachment, videoContent, vimeoContent and youTubeContent style set entries, which no longer affect rendering, and removed the unused webchat__chat-history-box__toolbar--rtl class, in PR #6024, by @OEvgeny

Description

These components still used emotion style sets and now use CSS Modules. No snapshot changes.

Design

• One PR for the 10 entries, as they share the pattern; the alternative is two PRs (media + videoHeight, and the other 4).
• The scroll-to-end toolbar is outside the transcript's dir, so it gets its own dir for inset-inline-end; the --rtl class goes.

Specific Changes

• ChatHistoryBox, ChatHistoryToolbar, ImageAvatar, ErrorBox: own *.module.css; the 6 media components: MediaAttachment.module.css; activities: BasicTranscript.module.css
• --webchat__height--video: CustomPropertyNames.ts, CSSCustomPropertiesContainer.tsx; @deprecated: createStyleSet.ts, StyleSet/*.ts
• Tests: rtl/scrollToEndButton.html (main: same pixels, :dir(rtl) fails), styleOptions/videoHeight.html (135 px; passes on main)

• I have added tests and executed them locally
• I have added .changelog/<PR#>-<slug>.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)

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