Add MAUI build queue to serialize platform builds

[jfversluis]

Summary

Adds build queue serialization for MAUI platform resources (Android, iOS, Mac Catalyst, Windows) that share the same project file. MSBuild cannot handle concurrent builds of the same project, causing intermittent file locking and XamlC assembly resolution failures. This PR serializes builds per-project using a semaphore.

Replaces #14945 (closed due to lost write access after dotnet to microsoft org migration). All review feedback from @davidfowl and @joperezr on #14945 has been addressed in this PR.

Key Changes

Build Queue (MauiBuildQueueEventSubscriber)

• Subscribes to BeforeResourceStartedEvent for MAUI platform resources
• Uses a per-project SemaphoreSlim(1,1) to serialize dotnet build commands
• Shows Queued and Building states in the dashboard while waiting/building
• Runs dotnet build as a subprocess with output piped to the resource logger
• 10-minute build timeout prevents hung builds from blocking the queue

DCP Launch Override (ProjectLaunchArgsOverrideAnnotation)

• New [Experimental("ASPIREMAUI001")] annotation overrides DCP default dotnet run with dotnet build /t:Run
• MAUI requires build /t:Run because dotnet run does not support the Run target needed for device deployment
• DCP still appends project path and --configuration automatically

Stop-While-Queued Support

• Replaces the default stop command with a queue-aware version
• Users can stop resources that are in Queued or Building state
• Cancels the per-resource CTS, which unblocks the semaphore wait or kills the build process
• Overrides DCP FailedToStart state to show Exited (user-initiated stop, not failure)

Post-Build Semaphore Hold

• After pre-build succeeds, the semaphore is held until DCP dotnet build /t:Run reaches a stable state
• Prevents concurrent MSBuild on shared dependency outputs (e.g., MauiServiceDefaults)
• Replay-safe predicate skips stale snapshots from WatchAsync on resource restart

Review feedback addressed (from #14945)

• Removed Assembly.GetEntryAssembly() configuration reading (davidfowl)
• Removed IDisposable from MauiBuildQueueAnnotation (joperezr)
• Added IOException catch for broken pipe in PipeOutputAsync
• Documented TOCTOU race in stop command handler
• Used KnownResourceStates constants instead of string literals
• Marked ProjectLaunchArgsOverrideAnnotation with [Experimental("ASPIREMAUI001")]
• Added ReleaseSemaphoreSafely() helper to guard against ObjectDisposedException
• Replaced Task.Delay with deterministic WaitForBuildStartedAsync signals in tests

Testing

• 94 unit tests covering queue serialization, cancellation, timeouts, restart, multi-project concurrency, and edge cases
• Manual verification with the AspireWithMaui playground app

Files Changed

• src/Aspire.Hosting.Maui/Lifecycle/MauiBuildQueueEventSubscriber.cs - Core queue logic
• src/Aspire.Hosting.Maui/Annotations/MauiBuildQueueAnnotation.cs - Per-project queue state
• src/Aspire.Hosting.Maui/Annotations/MauiBuildInfoAnnotation.cs - Build metadata per resource
• src/Aspire.Hosting/ApplicationModel/ProjectLaunchArgsOverrideAnnotation.cs - DCP launch override
• src/Aspire.Hosting/Dcp/ExecutableCreator.cs - Reads override annotation
• tests/Aspire.Hosting.Maui.Tests/MauiBuildQueueTests.cs - 94 tests

[github-actions]

🚀 Dogfood this PR with:

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Or

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[Copilot]

Pull request overview

This PR introduces build-queue serialization for .NET MAUI platform resources that share the same project file, preventing concurrent MSBuild executions that can intermittently fail due to file locking and XamlC resolution issues.

Changes:

• Added a per-project build queue (semaphore) and lifecycle subscriber that runs a pre-build step and shows Queued/Building dashboard states.
• Added a ProjectLaunchArgsOverrideAnnotation and DCP support to override default dotnet run invocation (e.g., to dotnet build /t:Run for MAUI).
• Added extensive unit tests plus small updates to the MAUI playground and package/test warning suppressions.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
tests/Aspire.Hosting.Maui.Tests/MauiBuildQueueTests.cs	Adds unit tests for queueing/serialization, cancellation, restart behavior, and related edge cases.
tests/Aspire.Hosting.Maui.Tests/Aspire.Hosting.Maui.Tests.csproj	Suppresses ASPIREMAUI001 warning for the test project.
src/Aspire.Hosting/Dcp/DcpExecutor.cs	Adds support for overriding the base dotnet command args via annotation.
src/Aspire.Hosting/ApplicationModel/ProjectLaunchArgsOverrideAnnotation.cs	New annotation type used to override DCP-generated project launch args.
src/Aspire.Hosting.Maui/README.md	Documents the MAUI build queue behavior and architecture.
src/Aspire.Hosting.Maui/MauiProjectResourceExtensions.cs	Eagerly adds the per-project build queue annotation during AddMauiProject.
src/Aspire.Hosting.Maui/MauiPlatformHelper.cs	Configures MAUI platform resources to use launch-args override and adds build metadata annotation.
src/Aspire.Hosting.Maui/MauiHostingExtensions.cs	Registers the new MAUI build-queue event subscriber.
src/Aspire.Hosting.Maui/Lifecycle/MauiBuildQueueEventSubscriber.cs	Implements queued/building states, pre-build subprocess, cancellation, and post-build semaphore hold.
src/Aspire.Hosting.Maui/Aspire.Hosting.Maui.csproj	Suppresses ASPIREMAUI001 warning for the MAUI hosting package.
src/Aspire.Hosting.Maui/Annotations/MauiBuildQueueAnnotation.cs	Adds per-project semaphore and cancellation tracking.
src/Aspire.Hosting.Maui/Annotations/MauiBuildInfoAnnotation.cs	Adds per-resource build metadata used by the build-queue subscriber.
playground/AspireWithMaui/AspireWithMaui.MauiClient/MauiProgram.cs	Updates service base address scheme to https+http:// for HTTP fallback.
playground/AspireWithMaui/AspireWithMaui.MauiClient/AspireWithMaui.MauiClient.csproj	Updates several package references to stable versions.