fix(build): apply centralized TFM variables to all project files

- Update Roslyn projects to use $(RoslynTfm) instead of hardcoded netstandard2.0
- Update test project to use $(TestTfms) instead of hardcoded net8.0
- Update MAUI project to use $(MauiTfms) instead of hardcoded net8.0-*
- Remove conditional Windows TFM line (now handled by MauiTfms variable)

All 33 tests pass on net8.0, net9.0, and net10.0 RC2.

Co-authored-by: glennawatson <[email protected]>

Author: Copilot

src/ReactiveUI.SourceGenerator.Tests/ReactiveUI.SourceGenerators.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>$(TestTfms)</TargetFrameworks>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <LangVersion>13.0</LangVersion>

src/ReactiveUI.SourceGenerators.Analyzers.CodeFixes/ReactiveUI.SourceGenerators.Analyzers.CodeFixes.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFramework>$(RoslynTfm)</TargetFramework>
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>

src/ReactiveUI.SourceGenerators.Execute.Maui/ReactiveUI.SourceGenerators.Execute.Maui.csproj

@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net8.0-android;net8.0-ios;net8.0-maccatalyst</TargetFrameworks>
-    <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net8.0-windows10.0.19041.0</TargetFrameworks>
+    <TargetFrameworks>$(MauiTfms)</TargetFrameworks>
     <UseMaui>true</UseMaui>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>

src/ReactiveUI.SourceGenerators.Roslyn4120/ReactiveUI.SourceGenerators.Roslyn4120.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFramework>$(RoslynTfm)</TargetFramework>
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>

src/ReactiveUI.SourceGenerators.Roslyn480/ReactiveUI.SourceGenerators.Roslyn480.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFramework>$(RoslynTfm)</TargetFramework>
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>

src/ReactiveUI.SourceGenerators/ReactiveUI.SourceGenerators.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFramework>$(RoslynTfm)</TargetFramework>
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>