fix(combo-box): align invalid style and ai-label position

[heloiselui]

Closes #20120
Closes #20849

Fixes issues with Combobox invalid and warn icon positioning and AI label missing gradient and spacing.

Changelog

New

• Added divider between AI label and other icons inside the input field.
• Add controls in Combobox storybook.

Changed

• Fixed invalid icon position when paired with an AI label.
• Updated AI label styling to include gradient and blue color.
• Adjusted spacing between AI label, invalid icon, and chevron icons.

Removed

• Old Combobox input markup that caused misalignment.

Testing / Reviewing

• Go to WC Deploy Preview > Combobox > Default & With Ai Label.
• Verify if Combobox looks similar to the expected image (this is from MultiSelect, designs needs confirm if is ok):
• Invalid/warn states in Default and With Ai Label stories should fit the design spec.

e.g:

• For the AI Label is missing gradient style, please check if:
  • The blue AI styling/colors appearing on the input.
  • A divider between the AI decorator and the chevron in the input.
  • When the close icon appears in the input, the spacing is off and there should be a divider between the AI decorator and the close icon in the input.

e.g:

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 92.33%. Comparing base (7a12453) to head (9da6b40).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #20978   +/-   ##
=======================================
  Coverage   92.33%   92.33%           
=======================================
  Files         511      511           
  Lines       37341    37341           
  Branches     5677     5738   +61     
=======================================
  Hits        34478    34478           
+ Misses       2715     2714    -1     
- Partials      148      149    +1     

Flag	Coverage Δ
main-packages	85.49% <ø> (ø)
web-components	96.66% <ø> (ø)

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