Improve shutdown sequence of Aspire service and fix race condition

[tmat]

Fixes intermittent test failure observed in #53424

Also fixes error reporting when expected exception is thrown after pipe disposal. This is a regression introduced by refactoring of named pipe transport

[Copilot]

Pull request overview

This is a large PR that refactors the dotnet-watch Aspire integration to support macOS (and other non-Windows platforms), introduces a new three-process architecture for Aspire watch (host, server, resource), and modernizes the test infrastructure. Previously, several Aspire-related tests were restricted to Windows via PlatformSpecificFact. The PR also introduces status reporting and control command pipes for communication between the Aspire host and watch server.

Changes:

• Refactors Aspire watch into a three-process model (host, server, resource launchers) communicating via named pipes, replacing the old DotNetWatchLauncher/DotNetWatchOptions with command-based CLI (server, resource, host subcommands) and adds status/control pipe support.
• Overhauls EnvironmentOptions to derive the muxer path from SdkDirectory instead of accepting it directly, adds a configurable LogMessagePrefix, introduces notification-only MessageDescriptors (LogLevel.None), and updates ProjectRepresentation to a record struct with OS-aware path equality.
• Modernizes test infrastructure by replacing IDisposable with IAsyncDisposable, moving from BufferBlock to Channel<T> in AwaitableProcess, extracting TestEventObserver from TestReporter, splitting large test classes into focused files, and removing Windows-only test restrictions.

Reviewed changes

Copilot reviewed 93 out of 94 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
src/Dotnet.Watch/Watch/Context/EnvironmentOptions.cs	Replace MuxerPath with SdkDirectory; derive muxer path from SDK dir
src/Dotnet.Watch/Watch/Context/EnvironmentVariables.cs	Add ReadTimeSpanSeconds helper
src/Dotnet.Watch/Watch/Build/ProjectRepresentation.cs	Convert to record struct with OS-aware equality on ProjectGraphPath
src/Dotnet.Watch/Watch/UI/IReporter.cs	Add notification-only MessageDescriptors, configurable log prefix
src/Dotnet.Watch/Watch/UI/ConsoleReporter.cs	Accept logMessagePrefix parameter
src/Dotnet.Watch/dotnet-watch/Program.cs	Use new EnvironmentOptions API; accept ILoggerFactory
src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs	Refactor build to emit notifications; centralize restart logic
src/Dotnet.Watch/Watch/HotReload/CompilationHandler.cs	OS-aware path comparers; new RestartPeripheralProjectsAsync
src/Dotnet.Watch/Watch/Process/RunningProject.cs	Change RestartOperation to ValueTask; add RestartAsync
src/Dotnet.Watch/Watch/Process/ProjectLauncher.cs	Expose CompilationHandler; use GetMuxerPath()
src/Dotnet.Watch/Watch/Aspire/AspireServiceFactory.cs	Return ValueTask from StartProjectAsync
src/Dotnet.Watch/Watch.Aspire/AspireLauncher.cs	New base class for Aspire launchers with CLI parsing
src/Dotnet.Watch/Watch.Aspire/Server/AspireServerLauncher.cs	New server launcher with status/control pipes
src/Dotnet.Watch/Watch.Aspire/Server/ProcessLauncherFactory.cs	Named pipe listener accepting resource launch requests
src/Dotnet.Watch/Watch.Aspire/Server/WatchStatusWriter.cs	Writes status events to named pipe
src/Dotnet.Watch/Watch.Aspire/Server/WatchControlReader.cs	Reads control commands (e.g., rebuild) from pipe
src/Dotnet.Watch/Watch.Aspire/Server/StatusReportingLoggerFactory.cs	Intercepts log events for status reporting
src/Dotnet.Watch/Watch.Aspire/Resource/AspireResourceLauncher.cs	Resource process connecting to server pipe
src/Dotnet.Watch/Watch.Aspire/Host/AspireHostLauncher.cs	Host launcher for single-project watch
src/Dotnet.Watch/Watch.Aspire/Commands/*.cs	CLI command definitions for server, resource, host
src/Dotnet.Watch/Watch.Aspire/Program.cs	Rewritten entry point dispatching to launcher
test/.../AwaitableProcess.cs	Replace BufferBlock with Channel<T>; async dispose
test/.../WatchableApp.cs	Generic launcher; async dispose; configurable executable
test/.../DotNetWatchTestBase.cs	IAsyncLifetime; CreateInProcWatcher factory
test/.../TestEventObserver.cs	Extracted event observation from TestReporter
Various test files	Split tests into focused files; remove Windows-only restrictions
test/.../AspireLauncherTests.cs	New integration test for server/resource communication
test/.../Aspire*CliTests.cs	CLI parsing tests for all three subcommands
src/Dotnet.Watch/.editorconfig	Suppress diagnostics for Watch solution

[tmat]

@DustinCampbell ptal
@mmitche FYI