Add geometry change invalidation support

[Kyle-Ye]

Agent Summary

This adds UIKit geometry-change registration hooks to hosting views so transform invalidation can respond when host geometry changes.

The update forwards _geometryChanged through _UIHostingView, lazily registers geometry observation when the root transform is requested, and unregisters when transform invalidation no longer needs observation. It also implements ViewGraph.invalidateTransform() so root transform state is invalidated and graph delegates are notified.

Validation:

• git diff --check
• swift build (passes with existing project warnings)

[codecov]

Codecov Report

❌ Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 26.94%. Comparing base (bc26339) to head (cf2628d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
Sources/OpenSwiftUICore/View/Graph/ViewGraph.swift	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #881      +/-   ##
==========================================
- Coverage   26.95%   26.94%   -0.01%     
==========================================
  Files         678      678              
  Lines       47139    47144       +5     
==========================================
- Hits        12705    12704       -1     
- Misses      34434    34440       +6     

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[augmentcode]

🤖 Augment PR Summary

Summary: Adds UIKit geometry-change hooks so hosting views can invalidate root transform state when host geometry changes.

Changes:

• Expose UIKit SPI for geometry change callbacks/registration in the UIKit shim header
• Forward `_geometryChanged(_:forAncestor:)` through _UIHostingView into UIHostingViewBase
• Lazily register for geometry changes when rootTransform() is requested
• Unregister geometry observation when transform invalidation no longer requires it
• Implement ViewGraph.invalidateTransform() to invalidate root transform and notify the graph delegate

Technical Notes: Geometry callbacks now trigger .transform invalidation, and safe-area invalidation is also updated when the container region isn’t present.

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[augmentcode]

Review completed. 2 suggestions posted.

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

[augmentcode]

In Sources/OpenSwiftUI/Integration/Hosting/UIKit/View/UIHostingViewBase.swift:253, if !wasRegisteredForGeometryChanges, registeredForGeometryChanges looks effectively unreachable because this method only ever sets registeredForGeometryChanges to false. Consider double-checking that this is actually protecting against the “incidental registration” case you’re trying to guard.

Severity: low

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[augmentcode]

In Sources/OpenSwiftUI/Integration/Hosting/UIKit/View/UIHostingView.swift:251, overriding UIKit’s _geometryChanged(_:forAncestor:) without calling super may suppress UIKit’s internal geometry propagation. Consider confirming that skipping super._geometryChanged is safe across the UIKit versions you’re targeting.

Severity: medium

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