Fix/hot reload shutdown

[DBeardionaire]

Connected HMR WebSockets can keep requests alive during application shutdown, delaying the host from stopping. I 1st saw this when using aspire rebuild/restart and then with dotnet run and Ctrl + C.

Registers the hot reload service with IHostApplicationLifetime.ApplicationStopping so shutdown aborts connected sockets and unsubscribes from build notifications. Guarded client registration so connections arriving during shutdown are also aborted, and reuse the cleanup during disposal.

Adds a component regression test that connects an HMR client, triggers application stopping, and verifies the service clears its connected clients.

[DBeardionaire]

I also see a test failing locally in LargeGraphTests that I didn't include in case it should be handled separately or is just failing on my machine

JsxCore/test/JsxCore.Tests/Unit/PackageManagement/Native/LargeGraphTests.cs

[Theory]
[InlineData("eslint")]
[InlineData("webpack")]
[InlineData("jest")]
public async Task Resolve_LargeGraph_ProducesATreeWhereEveryDependencyResolves(string package)
{
    var placed = await new PackageResolver(Registry()).ResolveAsync([new PackageRequest(package, "")]);

    placed.Count.ShouldBeGreaterThan(50);
    PackageResolver.Validate(placed).ShouldBeEmpty();
}