Add RedactedImage support

[Kyle-Ye]

No description provided.

[augmentcode]

🤖 Augment PR Summary

Summary: This PR adds core support for a redacted placeholder image, enabling image redaction to function end-to-end.

Changes:

• Implements GraphicsImage.redact(in:) to replace image contents with a low-opacity foreground color fill
• Adds Image.redacted backed by a new ImageProvider that resolves a 1×1 resizable color image
• Refactors CGImageProvider to reuse the new GraphicsImage.redact helper
• Updates the example app to show a new AsyncImageExample and switches the default ContentView sample

Technical Notes: The redaction color is derived from the resolved foreground color and multiplied by an opacity factor (0.16) to match existing redaction behavior.

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[augmentcode]

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 28.14%. Comparing base (a198635) to head (6a52218).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...UICore/Data/EnvironmentKeys/RedactionReasons.swift	0.00%	19 Missing ⚠️
...s/OpenSwiftUICore/View/Image/CGImageProvider.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #731      +/-   ##
==========================================
- Coverage   28.14%   28.14%   -0.01%     
==========================================
  Files         603      603              
  Lines       36941    36955      +14     
==========================================
+ Hits        10398    10400       +2     
- Misses      26543    26555      +12     

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