fix: make doc previews theme aware

[devadula-nandan]

Closes #20645

THESE ARE STORYBOOK ONLY STYLE UPDATES

Adds background to docs previews of the components so they show properly on every theme in storybook. both react and web-components

Changelog

New

• added theme background to .docs-story element in both web components and react

Testing / Reviewing

change theme to any other variant (more noticeable in dark variants) in storybook and observe all the stories docs pages in both react and web components render with proper background in the preview

PR Checklist

As the author of this PR, before marking ready for review, confirm you:

• Reviewed every line of the diff
• [ ] Updated documentation and storybook examples
• [ ] Wrote passing tests that cover this change
• [ ] Addressed any impact on accessibility (a11y)
• [ ] Tested for cross-browser consistency
• Validated that this code is ready for review and status checks should pass

More details can be found in the pull request guide

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.11%. Comparing base (30b4f87) to head (662fe90).
⚠️ Report is 261 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20647      +/-   ##
==========================================
+ Coverage   91.39%   92.11%   +0.71%     
==========================================
  Files         485      492       +7     
  Lines       31370    34352    +2982     
  Branches     5430     5586     +156     
==========================================
+ Hits        28670    31642    +2972     
- Misses       2547     2563      +16     
+ Partials      153      147       -6     

Flag	Coverage Δ
main-packages	85.34% <ø> (+0.40%)	⬆️
web-components	97.06% <ø> (-0.11%)	⬇️

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[devadula-nandan]

vrt shard 3/4 didn't complete
Error: page.goto: net::ERR_INSUFFICIENT_RESOURCES at http://localhost:3000/iframe?id=components-tabs--contained-full-width&viewMode=story&globals=theme:g10

can anyone restart it?

[emyarod]

looks good to me! I restarted the vrt job

[maradwan26]

LGTM