Add NamedColor support for macOS

[Kyle-Ye]

Summary

• Fix named color resolution on macOS by adding NSAppearanceName string mapping in CUICatalog.findAsset (previously only used UIAppearance strings from iOS)
• Add isUIKitBased() guard in resolveCGColor to use correct idiom/matchTypes on non-UIKit platforms (macOS native uses idiom 0 + .appearance match type)
• Add NamedColor example with 4 color swatches (light/dark × standard/increased contrast) and expanded asset catalog with distinct colors per appearance variant

Test plan

• Verify named color resolves correctly on macOS (was previously broken)
• Run NamedColorUITests snapshot test on both macOS and iOS
• Verify iOS named color resolution is unchanged

[augmentcode]

🤖 Augment PR Summary

Summary: This PR fixes named color resolution on macOS by aligning CoreUI asset lookups with AppKit appearance naming.

Changes:

• Update CUICatalog.findAsset to map environment appearance/contrast to NSAppearanceName… strings when the catalog uses AppKit appearance names.
• Adjust named color resolution to choose idiom/match-types based on isUIKitBased(); macOS-native paths use appearance-only matching.
• Refine CoreUI match-type defaults to include an explicit Vision idiom match (then appearance) for Vision assets.
• Add a new NamedColorExample view showing light/dark × standard/increased-contrast swatches.
• Expand the example asset catalog to include distinct colors per appearance/contrast variant (including mac idiom entries).
• Update snapshot UI tests to render the new example and re-enable the test on macOS.

Technical Notes: The macOS fix hinges on using the correct CoreUI appearance-name strings (NSAppearance vs UIAppearance) and ensuring the match-type list is non-empty on non-UIKit platforms.

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[augmentcode]

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[codecov]

Codecov Report

❌ Patch coverage is 44.11765% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 27.49%. Comparing base (e04fe6b) to head (8cbe696).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ces/OpenSwiftUICore/Graphic/Color/NamedColor.swift	40.00%	18 Missing ⚠️
...ources/OpenSwiftUICore/Graphic/CatalogLookup.swift	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #819      +/-   ##
==========================================
+ Coverage   27.48%   27.49%   +0.01%     
==========================================
  Files         661      661              
  Lines       42425    42444      +19     
==========================================
+ Hits        11660    11671      +11     
- Misses      30765    30773       +8     

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