refactor: isolate scheduler state and condense code comments

CLAUDE.md

@@ -134,12 +134,11 @@ dotnet test "tests/ReactiveUI.Primitives.Async.Tests/ReactiveUI.Primitives.Async
   --treenode-filter "/*/*/*/Async"
 ```
 
-### API Approval Notes
+### Public API Checks
 
-- API approval baselines live under `src/tests/**/ApiApprovalTests.*.verified.txt`
-- New TFMs usually require corresponding new `DotNet11_0.verified.txt` files
-- If approval tests fail with `.received.txt` output, inspect the generated snapshot and promote it intentionally if the
-  API change is expected
+- `PublicApiSharp.Analyzers` checks each package's `src/<Project>/PublicAPI/<tfm>/PublicAPI.txt` baseline.
+- New target frameworks require a corresponding baseline directory.
+- For an intentional API change, review the affected signatures and update the corresponding framework baselines.
 
 ---
 

src/Directory.Packages.props

@@ -33,7 +33,6 @@
   </ItemGroup>
   <ItemGroup>
     <PackageVersion Include="Avalonia" Version="$(AvaloniaVersion)"/>
-    <PackageVersion Include="Avalonia.Headless" Version="$(AvaloniaVersion)"/>
     <PackageVersion Include="Microsoft.AspNetCore.Components" Version="8.0.31" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0')) AND !$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))"/>
     <PackageVersion Include="Microsoft.AspNetCore.Components" Version="9.0.20" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0')) AND !$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net10.0'))"/>
     <PackageVersion Include="Microsoft.AspNetCore.Components" Version="10.0.12" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net10.0')) AND !$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net11.0'))"/>

src/Polyfills/ArgumentExceptionHelper.cs

@@ -7,11 +7,7 @@
 
 namespace ReactiveUI.Primitives.Internal;
 
-/// <summary>
-/// Polyfill for <c>ArgumentNullException.ThrowIfNull</c> on target frameworks (net462-net481) that predate it.
-/// On net8.0 and later this type is not compiled; consuming projects alias the <c>ArgumentExceptionHelper</c>
-/// identifier directly to <see cref="ArgumentNullException"/> so the call sites bind to the BCL method.
-/// </summary>
+/// <summary>Polyfill for <c>ArgumentNullException.ThrowIfNull</c> on target frameworks that predate it.</summary>
 [ExcludeFromCodeCoverage]
 internal static class ArgumentExceptionHelper
 {

src/Polyfills/ArgumentOutOfRangeExceptionHelper.cs

@@ -70,9 +70,7 @@ internal static void ThrowIfLessThan(
         "Design",
         "SST2318:Members should not have identical bodies",
         Justification =
-            "A type-specialized polyfill overload. The bounds-check body is identical to the int overload only "
-            + "because the guard shape is the same; the two operate on different value types (int vs TimeSpan) and "
-            + "cannot forward to one another. This mirrors the BCL's per-type ThrowIfLessThan overloads.")]
+            "The int and TimeSpan overloads guard different value types and cannot forward to one another.")]
     internal static void ThrowIfLessThan(
         TimeSpan value,
         TimeSpan other,

src/Polyfills/ObjectDisposedExceptionHelper.cs

@@ -6,11 +6,7 @@
 
 namespace ReactiveUI.Primitives.Internal;
 
-/// <summary>
-/// Polyfill for <c>ObjectDisposedException.ThrowIf</c> on target frameworks (net462-net481) that predate it.
-/// On net8.0 and later this type is not compiled; consuming projects alias the <c>ObjectDisposedExceptionHelper</c>
-/// identifier directly to <see cref="ObjectDisposedException"/> so the call sites bind to the BCL method.
-/// </summary>
+/// <summary>Polyfill for <c>ObjectDisposedException.ThrowIf</c> on target frameworks that predate it.</summary>
 [ExcludeFromCodeCoverage]
 internal static class ObjectDisposedExceptionHelper
 {

src/Polyfills/TaskCompletionSource.cs

@@ -19,7 +19,7 @@ internal sealed class TaskCompletionSource
 
     /// <summary>Initializes a new instance of the <see cref="TaskCompletionSource"/> class.</summary>
     [SuppressMessage("Concurrency", "PSH1302", Justification =
-        "BCL-parity polyfill; must match the framework ctor's TaskCreationOptions.None default, not force async continuations.")]
+        "Matches the framework constructor's TaskCreationOptions.None default.")]
     public TaskCompletionSource() => _inner = new();
 
     /// <summary>Transitions the underlying task to the <see cref="TaskStatus.RanToCompletion"/> state.</summary>
@@ -47,9 +47,7 @@ internal sealed class TaskCompletionSource
         "Design",
         "SST2318:Members should not have identical bodies",
         Justification =
-            "Distinct BCL-parity surface members with different contracts and return types: SetCanceled is void and "
-            + "TrySetCanceled returns bool. They share the same backing call here but must track the framework surface "
-            + "independently, so they are deliberately kept as separate members rather than one forwarding to the other.")]
+            "SetCanceled returns void and TrySetCanceled returns bool; each tracks its own framework contract.")]
     internal bool TrySetCanceled() => _inner.TrySetCanceled();
 
     /// <summary>Attempts to transition the underlying task to the <see cref="TaskStatus.Canceled"/> state for the specified token.</summary>

src/Polyfills/TaskPolyfillExtensions.cs

@@ -58,7 +58,7 @@ private static async Task WaitForCompletionAsync(Task task, TimeSpan timeout, Ca
         using var linked = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
         if (timeout != Timeout.InfiniteTimeSpan)
         {
-            linked.CancelAfter(timeout);
+            ScheduleTimeout(linked, timeout);
         }
 
         using (linked.Token.Register(static state => ((TaskCompletionSource<bool>)state).TrySetResult(true), signal))
@@ -71,5 +71,12 @@ private static async Task WaitForCompletionAsync(Task task, TimeSpan timeout, Ca
             }
         }
     }
+
+    /// <summary>Schedules cancellation when the timeout elapses.</summary>
+    /// <param name="source">The cancellation source.</param>
+    /// <param name="timeout">The timeout duration.</param>
+    [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
+    private static void ScheduleTimeout(CancellationTokenSource source, TimeSpan timeout) => source.CancelAfter(timeout);
 }
 #endif

src/Primitives.Async.Shared/Advanced/StartSubscription.cs

@@ -46,7 +46,21 @@ protected override async ValueTask ExecuteAsyncCore(
             return;
         }
 
-        await Task.Factory.StartNew(
+        await ExecuteOnSchedulerAsync(observer, taskScheduler, cancellationToken).ConfigureAwait(false);
+    }
+
+    /// <summary>Starts the action through the supplied scheduler.</summary>
+    /// <param name="observer">The observer receiving the signal notification.</param>
+    /// <param name="taskScheduler">The scheduler that starts the action.</param>
+    /// <param name="cancellationToken">Cancellation for the scheduled task and notifications.</param>
+    /// <returns>The scheduled action and notification operation.</returns>
+    [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
+    private Task ExecuteOnSchedulerAsync(
+        IObserverAsync<RxVoid> observer,
+        TaskScheduler taskScheduler,
+        CancellationToken cancellationToken) =>
+        Task.Factory.StartNew(
                 static s =>
                 {
                     var (self, observer, cancellationToken) =
@@ -57,9 +71,7 @@ await Task.Factory.StartNew(
                 cancellationToken,
                 TaskCreationOptions.DenyChildAttach,
                 taskScheduler)
-            .Unwrap()
-            .ConfigureAwait(false);
-    }
+            .Unwrap();
 
     /// <summary>Runs the action and forwards the completion signal.</summary>
     /// <param name="observer">The observer receiving the signal notification.</param>