Add DisplayList async platform updates

[Kyle-Ye]

Summary

• Add the initial DisplayList view render/update pipeline, including DisplayListViewModel, view cache, platform update paths, and nextUpdate support.
• Add async platform update plumbing for item, state, geometry, clip, shape, shadow, and child traversal updates.
• Add shape/mask layer support plus QuartzCore shims for backdrop/private CALayer behavior.
• Update image/text rendering helpers, geometry utilities, examples, and Xcode schemes for the new render path.
• Keep Linux builds working by guarding QuartzCore-only APIs and adding a non-CoreGraphics CGPath bounding rect fallback.

[augmentcode]

🤖 Augment PR Summary

Summary: This PR introduces an initial DisplayList-driven view render/update pipeline and adds “next update” scheduling support for dynamic content.

Changes:

• Implements DisplayList view update paths in DisplayListViewPlatform (content/effect kinds, drawing views, shape/shadow, platform views/layers).
• Adds async platform-update plumbing via AsyncLayer properties and update helpers (geometry, opacity, transforms, clips/masks, shadows).
• Adds DisplayList.nextUpdate(after:) and per-item nextUpdate propagation to drive scheduled updates.
• Extends TimelineSchedule with nextEntry and wires Text rendering to compute its next scheduled update.
• Introduces QuartzCore shims/support for backdrop layers and begins stubbing async updates for filters/images/clips.
• Updates example schemes and an async render example to support the new render path (including an OpenSwiftUI/SwiftUI import switch).

Technical Notes: Several async update helpers currently return “not supported” (false) to trigger fallback; QuartzCore-only behavior is guarded to keep non-Darwin builds viable.

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[augmentcode]

Review completed. 2 suggestions posted.

Comment augment review to trigger a new review at any time.

[augmentcode]

Sources/OpenSwiftUICore/Render/DisplayList/DisplayListViewPlatform.swift:2008 — forEachChild no longer has the #if canImport(Darwin) guard, but subviews(_:) / maskView(_:) still call _openSwiftUIPlatformUnimplementedFailure() when QuartzCore isn’t available. If this path executes on Linux/non-QuartzCore platforms it looks like a runtime trap/regression compared to the previous no-op behavior.

Severity: medium

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[augmentcode]

Sources/OpenSwiftUICore/Render/DisplayList/DisplayListViewPlatform.swift:1858 — asyncLayer.layer.mask! is force-unwrapped; if a .mask layer ever exists without a configured mask (or if mask setup lags behind bounds updates), this will crash instead of falling back to a non-async path.

Severity: medium

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 962 lines in your changes missing coverage. Please review.
✅ Project coverage is 25.69%. Comparing base (a6adab4) to head (bbfe7bf).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...e/Render/DisplayList/DisplayListViewPlatform.swift	0.00%	761 Missing ⚠️
...enSwiftUICore/Render/DisplayList/DisplayList.swift	0.00%	98 Missing ⚠️
Sources/OpenSwiftUICore/Shape/ShapeLayer.swift	0.00%	44 Missing ⚠️
...ore/Render/DisplayList/DisplayListAsyncLayer.swift	0.00%	35 Missing ⚠️
...ces/OpenSwiftUICore/View/Text/Text/Text+View.swift	0.00%	8 Missing ⚠️
...ftUICore/Animation/Timeline/TimelineSchedule.swift	0.00%	5 Missing ⚠️
...tUICore/Shape/ShapeStyle/ShapeStyleRendering.swift	0.00%	5 Missing ⚠️
Sources/OpenSwiftUICore/Shape/MaskLayer.swift	0.00%	3 Missing ⚠️
...ources/OpenSwiftUICore/View/Image/ImageLayer.swift	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #861      +/-   ##
==========================================
- Coverage   26.18%   25.69%   -0.49%     
==========================================
  Files         677      677              
  Lines       46059    46905     +846     
==========================================
- Hits        12059    12053       -6     
- Misses      34000    34852     +852     

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