Implement partial solution update support and fix bugs

[tmat]

Switches to new Roslyn APIs for committing/discarding solution update and completes implementation of partial solution update: dotnet/roslyn#78244.

Fixes issue causing stale warnings being reported when updating document after rebuilding project. The updated document didn't get checksum algorithm set correctly, which caused mismatch.

[Copilot]

Pull Request Overview

This PR implements partial solution update support using new Roslyn APIs and fixes stale warnings by preserving document checksum information.

• Refactors IncrementalMSBuildWorkspace and CompilationHandler to use GetSourceTextAsync with encoding and checksum, and to call commit/discard on hot-reload updates.
• Updates HotReloadDotNetWatcher to remove legacy baseline methods and adopt the new prompt signature.
• Expands test coverage and utilities: enhances test logging, adds new Aspire no-effect auto-restart tests, and scaffolds a Web project in TestAssets.

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/dotnet-watch.Tests/Watch/Utilities/WatchableApp.cs	Added ASPIRE_ALLOW_UNSECURED_TRANSPORT environment variable for Aspire scenarios.
test/dotnet-watch.Tests/Watch/Utilities/DotNetWatchTestBase.cs	Enhanced Log and UpdateSourceFile to capture caller file/line context.
test/dotnet-watch.Tests/HotReload/CompilationHandlerTests.cs	Updated CompilationHandler constructor usage.
test/dotnet-watch.Tests/HotReload/ApplyDeltaTests.cs	Replaced direct Logger.WriteLine calls with contextual Log and expanded tests.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.Web/appsettings.json	Added default logging configuration.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.Web/appsettings.Development.json	Added development logging configuration.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.Web/WatchAspire.Web.csproj	Scaffolds new Web project.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.Web/Properties/launchSettings.json	Defines HTTP/HTTPS launch profiles.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.Web/Program.cs	Adds minimal top-level Program.cs for Web project.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.Web/Components/PhotoList.razor	Adds sample Razor component with C#12 array initializer.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.AppHost/WatchAspire.AppHost.csproj	References Web project in AppHost.
test/TestAssets/TestProjects/WatchAspire/WatchAspire.AppHost/Program.cs	Updates DistributedApplication builder to include Web frontend.
src/BuiltInTools/dotnet-watch/Properties/launchSettings.json	Configures non-interactive mode and Aspire env var for built-in tool.
src/BuiltInTools/dotnet-watch/HotReloadDotNetWatcher.cs	Refactors hot-reload callback logic and removes obsolete baseline calls.
src/BuiltInTools/dotnet-watch/HotReload/IncrementalMSBuildWorkspace.cs	Updates GetSourceTextAsync to propagate encoding/checksum and uses C#12 syntax.
src/BuiltInTools/dotnet-watch/HotReload/CompilationHandler.cs	Adds static commit requirement, removes legacy methods, and integrates commit/discard logic.

Comments suppressed due to low confidence (3)

src/BuiltInTools/dotnet-watch/HotReloadDotNetWatcher.cs:291

• The callback FileChangedCallback is declared as void but now contains return statements that return a bool. You should update its signature to async Task<bool> FileChangedCallback(...) (or match the expected delegate) to avoid compile errors.

                                        question = "Do you want to restart these projects?";

src/BuiltInTools/dotnet-watch/HotReload/CompilationHandler.cs:267

• Using return ([], []); to return an empty ImmutableDictionary<ProjectId, string> and an empty ImmutableArray<RunningProject> is invalid syntax. Replace with (ImmutableDictionary<ProjectId, string>.Empty, ImmutableArray<RunningProject>.Empty).

                return ([], []);

src/BuiltInTools/dotnet-watch/Properties/launchSettings.json:6

• [nitpick] The workingDirectory is an absolute path that is environment-specific. Consider using a relative path or parameterizing this value to avoid breaking on different developer machines.

      "workingDirectory": "C:\\sdk1\\artifacts\\tmp\\Debug\\Aspire_BuildE---04F22750\\WatchAspire.AppHost",

[tmat]

@DustinCampbell ptal