Add Dev PowerShell preset and improve resource cleanup

---
- 🛠️ Added "Dev PowerShell" preset using Launch-VsDevShell.ps1 in Options.cs
- 🧹 Implemented Dispose override in OpenCommandLinePackage.cs to clean up _dte and Instance
- 🛡️ Improved null-checking in ExecuteFile to prevent errors when no ProjectItem is found
Fixes #96
Fixes #82

Author: madskristensen

src/OpenCommandLine/OpenCommandLinePackage.cs

@@ -65,11 +65,27 @@ protected override async Task InitializeAsync(CancellationToken cancellationToke
             mcs.AddCommand(exeItem);
         }
 
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                _dte = null;
+                Instance = null;
+            }
+
+            base.Dispose(disposing);
+        }
+
         private void ExecuteFile(object sender, EventArgs e)
         {
             ThreadHelper.ThrowIfNotOnUIThread();
 
             ProjectItem item = VsHelpers.GetProjectItem(_dte);
+            if (item == null)
+            {
+                return;
+            }
+
             string path = item.FileNames[1];
             string folder = Path.GetDirectoryName(path);
 

src/OpenCommandLine/Options.cs

@@ -32,9 +32,13 @@ private static void InitializePresets()
             string devPromptFile = installDir != null 
                 ? Path.Combine(installDir, @"..\Tools\VsDevCmd.bat") 
                 : "";
+            string launchDevShellPs1 = installDir != null
+                ? Path.Combine(installDir, @"..\Tools\Launch-VsDevShell.ps1")
+                : "";
 
             _defaultPresets["cmd"] = new Command("cmd.exe");
             _defaultPresets["Dev Cmd Prompt"] = new Command("cmd.exe", "/k \"" + devPromptFile + "\"");
+            _defaultPresets["Dev PowerShell"] = new Command("powershell.exe", "-ExecutionPolicy Bypass -NoExit -File \"" + launchDevShellPs1 + "\"");
             _defaultPresets["PowerShellCore"] = new Command("pwsh.exe", "-ExecutionPolicy Bypass -NoExit");
             _defaultPresets["PowerShell"] = new Command("powershell.exe", "-ExecutionPolicy Bypass -NoExit");
             _defaultPresets["PowerShell ISE"] = new Command("powershell_ise.exe");