style: change resize handler z-index

[erha19]

Types

• 💄 Style Changes

Background or solution

🤖 Generated by Copilot at f1fc1d1

• Increase z-index of horizontal and vertical resize handles to ensure visibility and accessibility (link)
• Remove z-index of diagonal resize handle to avoid conflicts and make consistent with other handles (link)
• Remove z-index of resize container to avoid conflicts and make consistent with other elements (link)

Before:

默认的 sticky-widget 层级为 11，会盖住默认拖动条

After:

Changelog

🤖 Generated by Copilot at f1fc1d1

This pull request enhances the resize component in core-browser by fixing some z-index issues and making the handles more consistent.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01 ⚠️

Comparison is base (86d94ed) 57.62% compared to head (f1fc1d1) 57.62%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2868      +/-   ##
==========================================
- Coverage   57.62%   57.62%   -0.01%     
==========================================
  Files        1336     1336              
  Lines       84013    84013              
  Branches    17465    17465              
==========================================
- Hits        48412    48411       -1     
- Misses      32357    32358       +1     
  Partials     3244     3244              

Flag	Coverage Δ
jsdom	52.65% <ø> (-0.01%)	⬇️
node	16.78% <ø> (ø)

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see 1 file with indirect coverage changes

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