chore: Apply flashbar new style in one-theme

[at-susie]

Description

Related links, issue #, if available: n/a

How has this been tested?

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• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.57%. Comparing base (6a213a0) to head (0b607b7).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4671   +/-   ##
=======================================
  Coverage   97.57%   97.57%           
=======================================
  Files         948      948           
  Lines       30491    30492    +1     
  Branches    11151    11151           
=======================================
+ Hits        29751    29752    +1     
- Misses        693      733   +40     
+ Partials       47        7   -40     

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[mxschll]

I don't understand why this existed before and we're removing it now.

[at-susie]

It's actually not a true removal but it's retargeted. The flashbar-icon button variant was switched from the inverted interactive tokens to the plain colorTextInteractive* ones in the constants.scss.

So the warning override had to move from ...InvertedDefault/Hover to ...Default/Hover the inverted overrides are now dead.

The warning flash is light in both modes, so we still pin to colorNeutral650/950 for dismiss-icon contrast.