Fix validation to use strict equality check for undefined

Changed condition from `!selectedFile.fsPath` to `selectedFile.fsPath === undefined`
to avoid incorrectly rejecting empty string paths which are valid for root directories.

Co-authored-by: vhvb1989 <24213737+vhvb1989@users.noreply.github.com>

Author: Copilot

ext/vscode/src/commands/cmdUtil.ts

@@ -28,7 +28,7 @@ export function validateFileSystemUri(
     selectedItem: vscode.Uri | TreeViewModel | undefined,
     commandName: string
 ): void {
-    if (selectedFile && !selectedFile.fsPath) {
+    if (selectedFile && selectedFile.fsPath === undefined) {
         context.errorHandling.suppressReportIssue = true;
         const itemType = isTreeViewModel(selectedItem) ? 'TreeViewModel' :
                         isAzureDevCliModel(selectedItem) ? 'AzureDevCliModel' :