Fix process cleanup timeout causing port binding errors in no-hot-reload mode

[Copilot]

Running dotnet watch run --no-hot-reload fails with "address already in use" errors after file changes because the process cleanup timeout was set to 0 seconds in no-hot-reload mode, force-killing the dev server before it could release network ports.

Changes

• EnvironmentOptions.cs: Remove conditional logic that returned TimeSpan.FromSeconds(0) for no-hot-reload mode. Always return 5-second default timeout regardless of hot reload state to allow graceful shutdown.

• EnvironmentOptionsTests.cs: Add tests verifying timeout behavior returns 5 seconds for both hot reload enabled/disabled cases, and respects environment variable overrides.

// Before
public TimeSpan GetProcessCleanupTimeout(bool isHotReloadEnabled)
    => ProcessCleanupTimeout ?? (isHotReloadEnabled ? TimeSpan.FromSeconds(5) : TimeSpan.FromSeconds(0));

// After  
public TimeSpan GetProcessCleanupTimeout(bool isHotReloadEnabled)
    => ProcessCleanupTimeout ?? TimeSpan.FromSeconds(5);

The DOTNET_WATCH_PROCESS_CLEANUP_TIMEOUT_MS environment variable can still override the default timeout.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[.NET10RC2] dotnet watch run --no-hot-reload fails</issue_title>
<issue_description>### Describe the bug
Running dotnet watch run --no-hot-reload does not work correctly, at least for blazor-wasm projects.
When a rebuild is triggered, it does not shut down the old dev server, causing the new one to fail with a bind error.

To Reproduce

• Create new blazor wasm app (ie. dotnet new blazorwasm -e -p --no-https)
• Run with watch: dotnet watch run -c Release --property WarningLevel=0 --no-hot-reload
• Open in browser
• Make a change to one of the .razor files (ie. Home.razor)
• Note that the server fails to start
• Reload the page, note that the browser console is spammed with integrity errors due to not being able to find files.

Exceptions (if any)

fail: Microsoft.Extensions.Hosting.Internal.Host[11]
      Hosting failed to start
      System.IO.IOException: Failed to bind to address http://[::]:5117: address already in use.
       ---> Microsoft.AspNetCore.Connections.AddressInUseException: Address already in use
       ---> System.Net.Sockets.SocketException (98): Address already in use
         at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, Boolean disconnectOnFailure, String callerName)
         at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
         at System.Net.Sockets.Socket.Bind(EndPoint localEP)
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketTransportOptions.CreateDefaultBoundListenSocket(EndPoint endpoint)
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketConnectionListener.Bind()
         --- End of inner exception stack trace ---
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketConnectionListener.Bind()
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketTransportFactory.BindAsync(EndPoint endpoint, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure.TransportManager.BindAsync(EndPoint endPoint, ConnectionDelegate connectionDelegate, EndpointConfig endpointConfig, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl.<>c__DisplayClass28_0`1.<<StartAsync>g__OnBind|0>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.AddressBinder.BindEndpointAsync(ListenOptions endpoint, AddressBindContext context, CancellationToken cancellationToken)
         --- End of inner exception stack trace ---
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.AddressBinder.BindEndpointAsync(ListenOptions endpoint, AddressBindContext context, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.ListenOptions.BindAsync(AddressBindContext context, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.AnyIPListenOptions.BindAsync(AddressBindContext context, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.AddressBinder.AddressesStrategy.BindAsync(AddressBindContext context, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl.BindAsync(CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl.StartAsync[TContext](IHttpApplication`1 application, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)
         at Microsoft.Extensions.Hosting.Internal.Host.<StartAsync>b__14_1(IHostedService service, CancellationToken token)
         at Microsoft.Extensions.Hosting.Internal.Host.ForeachService[T](IEnumerable`1 services, CancellationToken token, Boolean concurrent, Boolean abortOnFirstException, List`1 exceptions, Func`3 operation)

Further technical details

details of dotnet --info

``` .NET SDK: Version: 10.0.100-rc.2.25502.107 Commit: 89c8f6a112 Workload version: 10.0.100-manifests.0cee6f9c MSBuild version: 18.0.0-preview-25502-107+89c8f6a11

Runtime Environment:
OS Name: nixos
OS Version: 25.11
OS Platform: Linux
RID: linux-x64
Base Path: /nix/store/aj7lxjjn3rl2bazsv9p0dfnv069j6rsq-dotnet-sdk-10.0.100-rc.2.25502.107/share/dotnet/sdk/10.0.100-rc.2.25502.107/

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
Version: 10.0.0-rc.2.25502.107
Architecture: x64
Commit: 89c8f6a112

.NET SDKs installed:
10.0.100-rc.2.25502.107 [/nix/store/aj7lxjjn3rl2ba...

• Fixes [.NET10RC2] dotnet watch run --no-hot-reload fails #51476

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