feat: add windows path ext resolution

This resolves a problem where the file name of a script file was not correctly executed when passed without extension.

src/process/Command.Execute.cs

@@ -11,7 +11,6 @@ public sealed partial class Command
 		return process.MainModule?.FileName;
 	});
 
-	private static readonly string[] WindowsExecutableExtensions = ["exe", "cmd", "bat"];
 	private static readonly TimeSpan CancelWaitTimeout = TimeSpan.FromSeconds(5);
 
 	private static string? ProcessPath => ProcessPathLazy.Value;
@@ -71,8 +70,7 @@ public sealed partial class Command
 
 			// Don't do anything for fully qualified paths or paths that already have an extension specified.
 			// System.Diagnostics.Process knows how to handle those without our help.
-			if (Path.IsPathFullyQualified(TargetFilePath) ||
+			if (Path.IsPathFullyQualified(TargetFilePath) || !string.IsNullOrWhiteSpace(Path.GetExtension(TargetFilePath)))
-				!string.IsNullOrWhiteSpace(Path.GetExtension(TargetFilePath)))
 			{
 				return TargetFilePath;
 			}
@@ -82,7 +80,7 @@ public sealed partial class Command
 					   where Directory.Exists(probeDirPath)
 					   select Path.Combine(probeDirPath, TargetFilePath)
 					   into baseFilePath
-					   from extension in WindowsExecutableExtensions
+					   from extension in GetPathExtensions()
 					   select Path.ChangeExtension(baseFilePath, extension)
 				   ).FirstOrDefault(File.Exists) ??
 				   TargetFilePath;
@@ -112,6 +110,24 @@ public sealed partial class Command
 					}
 				}
 			}
+
+			static IEnumerable<string> GetPathExtensions()
+			{
+				if (System.Environment.GetEnvironmentVariable("PATHEXT")?.Split(Path.PathSeparator) is { } extensions)
+				{
+					foreach (var extension in extensions)
+					{
+						yield return extension;
+					}
+				}
+				else
+				{
+					yield return ".COM";
+					yield return ".EXE";
+					yield return ".BAT";
+					yield return ".CMD";
+				}
+			}
 		}
 	}