docs: Widget Builder & UI Kit Builder documentation improvements

[juhi-saha]

Summary

Final round of documentation improvements for the Widget Builder and UI Kit Builder sections, building on top of the existing improvements in docs/widget-builder-ui-kit-builder-improvement.

Changes

Widget Builder

• Updated widget overview Related Resources: added UI Kit Builder link, removed redundant widget cross-links
• Removed JavaScript Chat SDK from widget overview Related Resources (not directly relevant)
• Renamed 'visual UI Kit Builder' to 'UI Kit Builder' in widget Related Resources for consistency
• Simplified widget/html/overview.mdx layout

UI Kit Builder (React, Next.js, React Router)

• Replaced old builder screenshot with updated uikit-builder-preview.png across all pages
• Removed Frame wrapper from builder preview image to fix blue border rendering issue
• Streamlined overview pages (React, Next.js, React Router) — removed redundant content, tightened descriptions
• Fixed integration page formatting (code block indentation for TypeScript/JavaScript tabs)

Cross-cutting

• Updated builder preview image (images/uikit-builder-preview.png)
• Consistent formatting across all 3 framework variants and widget platform pages

Files Changed (16 files)

• chat-builder/react/overview.mdx
• chat-builder/react/integration.mdx
• chat-builder/nextjs/overview.mdx
• chat-builder/nextjs/integration.mdx
• chat-builder/react-router/overview.mdx
• chat-builder/react-router/integration.mdx
• widget/html/overview.mdx
• widget/shopify/overview.mdx
• widget/squarespace/overview.mdx
• widget/webflow/overview.mdx
• widget/wix/overview.mdx
• widget/wordpress/overview.mdx
• ui-kit/react/moved/builder-integration.mdx
• ui-kit/react/moved/builder-integration-nextjs.mdx
• ui-kit/react/moved/builder-integration-react-router.mdx
• images/uikit-builder-preview.png

Contributors

• Juhi Saha (@juhi.cometchat)