[Test] Fix color mismatch on UI Compacibility test case

[Kyle-Ye]

Close #340

[augmentcode]

🤖 Augment PR Summary

Summary: This PR fixes a UI snapshot mismatch caused by slight differences in color rounding between OpenSwiftUI and SwiftUI.

Changes:

• Removes the relaxed perceptualPrecision workaround from ZStackUITests now that color output should match
• Adds a small UITest-only initializer (C constructor + Swift entrypoint) that runs at load time
• Enables Color.Resolved._alignWithSwiftUIImplementation for the UI test target to match SwiftUI’s rounding behavior

Technical Notes: Initialization is performed via a C attribute((constructor)) that calls a Swift function exported with @_cdecl, and only mutates the alignment flag when OPENSWIFTUI is enabled.

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[augmentcode]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 14.25%. Comparing base (37596d3) to head (2f09c82).
⚠️ Report is 1 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (37596d3) and HEAD (2f09c82). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (37596d3)	HEAD (2f09c82)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #689       +/-   ##
===========================================
- Coverage   28.73%   14.25%   -14.49%     
===========================================
  Files         588      562       -26     
  Lines       35701    33064     -2637     
===========================================
- Hits        10259     4713     -5546     
- Misses      25442    28351     +2909     

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