Reconcile main and release/2.0-stable source trees

[shisan (qiutongMS)]

Description

Goal

Align main and release/2.0-stable to the same buildable source tree, while preserving both branches' histories in main.

Approach

Use release/2.0-stable as the baseline because the main delta is smaller. This reconciliation is organized into four reviewable commits:

1. [SOURCE] - Add 2 sample solutions, reconcile updates across 18 existing sample areas, and remove 10 retired sample solutions based on main, while retaining 4 stable-only sample areas.
2. [INTEGRATION] - Reconcile CPM, solution and WAP wiring, package identity, runtime initialization, and pipeline integration.
3. [MECHANICAL] - Apply six repository-wide rules for package migration, toolsets, C++20, and publish metadata. These changes can be reviewed by rule rather than file by file.
4. [SEMANTIC] - Apply the minimum behavioral adaptation required by the combined tree; only two files are changed.

Please review the four commits separately. Functional review should focus on [INTEGRATION] and [SEMANTIC]; [MECHANICAL] contains only repeatable bulk transformations.

[SOURCE] inventory

The source composition changes 562 paths relative to release/2.0-stable. Each resulting changed blob comes directly from the pinned main revision; retained stable content remains unchanged.

• Added from main:
  • WinForms XAML Islands, together with its supporting WinUI class library.
  • SecureUI.
• Major updates from main:
  • Islands: replace the older DrawingIsland, UXFrameworksOnIslands, and C++ SimpleIsland solutions with the WinForms XAML Islands sample and supporting WinUI class library.
  • WindowsML: bring in the current execution-provider, performance, model-management, diagnostics, and sample updates.
  • Input: add the Keyboard Shortcut Manager scenario.
  • Notifications: remove the retired Badge samples and retain the current App and Push implementations.
  • Windowing and AppLifecycle: bring in the current source and packaging layouts.
• Additional source synchronization: Composition, CustomControls, DeploymentManager, Insights, Installer, Mica, PhotoEditor, ResourceManagement, SelfContainedDeployment, TextRendering, Unpackaged, and Widgets.
• Removed to match main: 10 retired sample solutions: 4 BackgroundTask solutions, 3 older Islands solutions, 2 Notifications Badge solutions, and 1 Unpackaged WinForms solution.
• Retained from stable: the stable-only CameraCaptureUI, DynamicDependenciesSample, OAuth2Manager, and StoragePickers sample areas, plus the stable-evolved WindowsAIFoundry implementation.
• Repository-level source updates from main: sample feed hydration and restore tooling, build entry points, templates, and sample documentation.

Result

This PR merges integration/main-stable-reconciliation into release/2.0-stable. A follow-up PR will merge integration/main-stable-reconciliation-final into main.

The review and final branches contain exactly the same code. The final branch only adds the ancestry required to preserve both branch histories in main.

Target Release

2.0 Stable

Validation

• Source provenance, commit boundaries, CPM, solution/WAP references, and updater modes have been audited.
• The five external-WAP solutions build for x64 and ARM64 Release with valid package layouts.
• Full Aggregator pipeline validation is pending.

Checklist

• Samples build and run using the Visual Studio versions listed in the Windows development docs.
• Samples build and run on all supported platforms (x64, x86, ARM64) and configurations (Debug, Release).
• Samples set the minimum supported OS version to Windows 10 version 1809.
• Samples build clean with no warnings or errors.
• [For new samples]: Samples have completed the sample guidelines checklist and follow standardization/naming guidelines.
• Microsoft employees only: you can validate your changes by following the instructions here: https://www.osgwiki.com/wiki/WindowsAppSDK-Samples