Fix process cleanup timeout for no-hot-reload mode

Co-authored-by: tmat <41759+tmat@users.noreply.github.com>

Author: Copilot

src/BuiltInTools/dotnet-watch/CommandLine/EnvironmentOptions.cs

@@ -61,9 +61,8 @@ internal sealed record EnvironmentOptions(
         );
 
         public TimeSpan GetProcessCleanupTimeout(bool isHotReloadEnabled)
-            // If Hot Reload mode is disabled the process is restarted on every file change.
-            // Waiting for graceful termination would slow down the turn around.
-            => ProcessCleanupTimeout ?? (isHotReloadEnabled ? TimeSpan.FromSeconds(5) : TimeSpan.FromSeconds(0));
+            // Allow sufficient time for the process to exit gracefully and release resources (e.g., network ports).
+            => ProcessCleanupTimeout ?? TimeSpan.FromSeconds(5);
 
         private int _uniqueLogId;
 

test/dotnet-watch.Tests/CommandLine/EnvironmentOptionsTests.cs

@@ -3,6 +3,40 @@
 
 namespace Microsoft.DotNet.Watch.UnitTests;
 
+public class EnvironmentOptionsTests
+{
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void GetProcessCleanupTimeout_WithoutEnvironmentVariable_ReturnsDefaultTimeout(bool isHotReloadEnabled)
+    {
+        var envOptions = new EnvironmentOptions(
+            WorkingDirectory: "/test",
+            MuxerPath: "dotnet",
+            ProcessCleanupTimeout: null);
+
+        var timeout = envOptions.GetProcessCleanupTimeout(isHotReloadEnabled);
+
+        Assert.Equal(TimeSpan.FromSeconds(5), timeout);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void GetProcessCleanupTimeout_WithEnvironmentVariable_ReturnsSpecifiedTimeout(bool isHotReloadEnabled)
+    {
+        var customTimeout = TimeSpan.FromSeconds(10);
+        var envOptions = new EnvironmentOptions(
+            WorkingDirectory: "/test",
+            MuxerPath: "dotnet",
+            ProcessCleanupTimeout: customTimeout);
+
+        var timeout = envOptions.GetProcessCleanupTimeout(isHotReloadEnabled);
+
+        Assert.Equal(customTimeout, timeout);
+    }
+}
+
 public class BuildReporterTests
 {
     [Fact]