Add View.onPreferenceChange support

[Kyle-Ye]

Summary

• add View.onPreferenceChange(_:perform:) with preference value-change tracking and cycle handling
• add the private transactional preference-change overload that forwards the producing Transaction
• update preference-writing integration for the new action path
• add separate examples and UI test cases for the public and transactional APIs
• preserve shared availability configurations in the generated Example targets

This supersedes #926 and incorporates the initial implementation by @Dark-Existed.

Closes #925

Validation

• xcodebuild build -workspace Example/Example.xcworkspace -scheme OSUI_Example -configuration OpenSwiftUIDebug -destination 'generic/platform=iOS Simulator' CODE_SIGNING_ALLOWED=NO
• xcodebuild build -workspace Example/Example.xcworkspace -scheme SUI_Example -configuration SwiftUIDebug -destination 'generic/platform=iOS Simulator' CODE_SIGNING_ALLOWED=NO
• UI tests not run

[augmentcode]

🤖 Augment PR Summary

Summary: This PR completes View.onPreferenceChange support in OpenSwiftUI, including a transactional overload that forwards the producing Transaction.

Changes:

• Adds `View.onPreferenceChange(_:perform:)` with value-change tracking, reset-seed handling, and update-cycle detection.
• Introduces a transactional preference action modifier/binder that delivers both the new preference value and the corresponding `Transaction`.
• Updates preference-writing and scene preference integration to support the new preference-action path.
• Adds separate Example views plus UI tests for the public API and the transactional SPI API.
• Tweaks Example project file inclusion to keep shared availability configuration inputs stable.

Technical Notes: Action dispatch is enqueued via Update.enqueueAction, and cycle detection is reset on viewPhase.resetSeed to help prevent preference-driven update loops.

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[augmentcode]

Review completed. 1 suggestion posted.

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

[augmentcode]

@available(iOS 18.2, macOS 15.2, *) makes this symbol effectively available on tvOS/watchOS/visionOS at all versions; consider adding explicit availability for the other Apple platforms (or marking them unavailable) to avoid cross-platform build mismatches. (Also applies to the similar availability usage in the transactional example/test in this PR.)

Severity: medium

Other Locations

• Example/Shared/ViewModifier/TransactionalPreferenceActionModifierExample.swift:14
• Example/OpenSwiftUIUITests/Modifier/ViewModifier/PreferenceActionModifierUITests.swift:50

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 96 lines in your changes missing coverage. Please review.
✅ Project coverage is 25.87%. Comparing base (e2c69fa) to head (504f026).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ore/Data/Preference/PreferenceActionModifier.swift	0.00%	88 Missing ⚠️
...difier/SceneModifier/PreferenceSceneModifier.swift	0.00%	3 Missing ⚠️
...re/Data/Preference/PreferenceWritingModifier.swift	0.00%	3 Missing ⚠️
...difier/ViewModifier/PreferenceActionModifier.swift	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #937      +/-   ##
==========================================
- Coverage   25.92%   25.87%   -0.05%     
==========================================
  Files         721      723       +2     
  Lines       50788    50878      +90     
==========================================
- Hits        13165    13163       -2     
- Misses      37623    37715      +92     

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