Migrate to Uno.Sdk and Uno Platform 7.0

[MartinZikmund]

Recreates #305 (Migrate to Uno.Sdk) on top of #315 (.NET 10 SDK + build tooling), and targets Uno Platform 7.0 for the WinUI 3 flavor.

Based on #315 (this PR targets its branch, so the diff only shows the changes below). Supersedes #305.

What's in here

1. Uno.Sdk migration (from #305)

Squashed recreation of #305's final state onto #315 - see #305 for the full commit history. In short:

• New unified Uno.Sdk single-project gallery heads (ProjectHeads/AllComponents/Uno, ProjectHeads/SingleComponent/Uno) serving win32, linux, macos, wasm, android and ios on WinUI 3.
• win32, linux and macos are first-class MultiTargets, all served by the single Skia -desktop TFM.
• Scripts and CI derive the Uno.Sdk head from -MultiTargets / -WinUIMajorVersion.
• WinUI 2 keeps Uno 5.x (Uno.UI) and its classic heads.

Only conflict against #315 was global.json.

2. Uno Platform 7.0 for WinUI 3

• Uno.Sdk 7.0.0-dev.51, Uno.WinUI / Uno.WinUI.Lottie 7.0.0-dev.1656 (the version that Uno.Sdk pins), Uno.Fonts.Fluent 2.9.4 (what Uno.WinUI 7 depends on).
• Uno 7 ships net10.0 / net11.0 only, so WinUI 3 Uno targets move to .NET 10 (net10.0, net10.0-desktop, net10.0-browserwasm, net10.0-android, net10.0-ios).
• New UnoDotNetTargetFramework in AvailableTargetFrameworks.props picks net10.0 for WinUI 3 and keeps net9.0 for WinUI 2. Uno.UI (WinUI 2) stays on Uno 5.x / .NET 9.
• Mac Catalyst stays out of the WinUI 3 package surface only (Uno 7 removed it). WinUI 2 still builds -maccatalyst.
• NET10_0_OR_GREATER added to DefinedConstants.props.
• MSBuild.Sdk.Extras workaround: Extras infers net10.0 as .NETFramework,Version=v10.0. Its TFM check only reads the first digit (Compatibility with .NET 10 TFMs novotnyllc/MSBuildSdkExtras#305, still open). Library.props now sets TargetFrameworkIdentifier for .NET TFMs.
• Hot Design and App MCP are disabled on the Uno heads (UnoDisableHotDesign / UnoDisableMCPSupport). The versions pinned by Uno.Sdk 7.0.0-dev.51 still reference pre-7.0 Uno assemblies, which causes UNOB0023 at build and a hang at startup (7.0-dev: HotDesign, Toolkit and CommunityToolkit packages reference 'Uno'/'Uno.UI.Toolkit', which 7.0 no longer ships unoplatform/uno#24297). There's a TODO to re-enable them.
• The classic Wasm head imports WinUI.TargetVersion.props before the TFM props.
• ToolkitDocumentationRenderer.xaml sets Background on MarkdownTextBlock only on Windows. On Uno it's a TextBlock, which has no Background in WinUI, and Uno 7 removed it for parity.

3. RichTextBlock lights up on Uno 7

Uno 7 ships a full port of WinUI's RichTextBlock (unoplatform/uno#23731):

• Sample source-code viewer: on Uno WinUI 3 it now uses a RichTextBlock with ColorCode syntax highlighting, like the Windows heads, instead of a plain TextBlock. ColorCode.WinUI is Windows-only, so Polyfills/ColorCode/RichTextBlockFormatter.cs ports its formatter onto ColorCode.Core. Uno WinUI 2 keeps the TextBlock fallback.
• Docs renderer: on Uno WinUI 3, MarkdownTextBlock can now wrap the Labs MarkdownTextBlock (RichTextBlock-based), themed to match the Windows typography. Links open through the same handler as on Windows. This is opt-in through LabsMarkdownTextBlockVersion, because Labs doesn't ship Uno targets yet (CommunityToolkit/Labs-Windows draft linked below). Until then, Uno shows the plain-text fallback.

Validation

Against CommunityToolkit/Windows main + #862 + the companion changes (draft PR linked below), on Windows with .NET SDK 10.0.400:

• GenerateAllSolution.ps1 -MultiTargets win32 -WinUIMajorVersion 3 generated all project references. The final SlnGen step can't launch here because no Visual Studio is found.
• CommunityToolkit.App.Uno for net10.0-desktop: 0 errors. 22 components plus samples compile against Uno 7.0.0-dev.1656.
• The gallery runs on Uno 7 Desktop (Win32 / Skia): shell, navigation, search and sample pages work. The sample code viewer shows syntax-highlighted XAML/C# in a RichTextBlock. A Debug launch takes ~30-60 s before the window appears.
• For that local run, Uno.Microsoft.Xaml.Behaviors.Interactivity.WinUI came from a local pack of feat: Update to Uno Platform 7.0 unoplatform/Uno.XamlBehaviors#36. No Uno 7 build of it is published yet (see below).

Consumer (CommunityToolkit/Windows) changes needed

Draft: CommunityToolkit/Windows#880

• global.json: .NET SDK 10.0.401, MSBuild.Sdk.Extras 3.0.44, Uno.Sdk 7.0.0-dev.51. Also bump component csprojs that still pin MSBuild.Sdk.Extras/3.0.23.
• Uno 7 source fixes: the class, DependencyObject constraints in DependencyObjectExtensions (DependencyObject is a class in Uno 7), the InsertExpressionKeyFrame nullable easing, and a TokenizingTextBoxAutomationPeer.GetChildrenCore shim until fix(automation): Align ListViewBaseAutomationPeer.GetChildrenCore return type with WinUI unoplatform/uno#25141 ships.

Upstream blockers and fixes

• Uno.XamlBehaviors has no Uno 7 build. feat: Update to Uno Platform 7.0 unoplatform/Uno.XamlBehaviors#36 adds it (CI green, verified locally against this gallery). We need its 4.0 package published, then bump Uno.Microsoft.Xaml.Behaviors.Interactivity.WinUI here and in Windows.
• ListViewBaseAutomationPeer.GetChildrenCore() returns List<> instead of WinUI's IList<>. Fixed in fix(automation): Align ListViewBaseAutomationPeer.GetChildrenCore return type with WinUI unoplatform/uno#25141 (closes [Skia/macOS] TokenizingTextBox crashes with TypeLoadException: incompatible GetChildrenCore return type unoplatform/uno#24552), together with a sync-generator check for this kind of override type mismatch.
• Uno.Sdk 7 dev pins pre-7 Hot Design / App MCP. Tracked in 7.0-dev: HotDesign, Toolkit and CommunityToolkit packages reference 'Uno'/'Uno.UI.Toolkit', which 7.0 no longer ships unoplatform/uno#24297.

Follow-ups

Once RichEditBox lands in Uno:

• RichSuggestBox (components/RichSuggestBox, currently uwp;wasdk): enable wasm;win32;linux;macos;ios;android on WinUI 3.

RichTextBlock-based:

• Labs MarkdownTextBlock on Uno (CommunityToolkit/Labs-Windows draft, in progress). Once it's published, set LabsMarkdownTextBlockVersion in App.Head.Uno.WinUI.Dependencies.props.
• Consider moving the Windows heads from the 7.x CommunityToolkit.WinUI.UI.Controls.Markdown to the Labs MarkdownTextBlock as well. That means replacing the 7.x win:Style with MarkdownThemes. Labs' UWP package has no uap10.0 target.

Housekeeping:

• Bump Uno.Microsoft.Xaml.Behaviors.Interactivity.WinUI once Uno.XamlBehaviors#36 is published.
• Re-enable Hot Design / App MCP once Uno 7-compatible builds ship.
• Drop the Extras TargetFrameworkIdentifier workaround once MSBuildSdkExtras#305 is fixed.
• Bump to Uno 7.0 stable once released.

🤖 Generated with Claude Code

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