don't add \ if path already starts with that on pwsh for suggestions (microsoft#251219)

fix microsoft#25127

Author: meganrogge

src/vs/workbench/contrib/terminalContrib/suggest/browser/terminalCompletionService.ts

@@ -525,6 +525,9 @@ function getFriendlyPath(uri: URI, pathSeparator: string, kind: TerminalCompleti
  */
 function addPathRelativePrefix(text: string, resourceRequestConfig: Pick<TerminalResourceRequestConfig, 'pathSeparator'>, lastWordFolderHasDotPrefix: boolean): string {
 	if (!lastWordFolderHasDotPrefix) {
+		if (text.startsWith(resourceRequestConfig.pathSeparator)) {
+			return `.${text}`;
+		}
 		return `.${resourceRequestConfig.pathSeparator}${text}`;
 	}
 	return text;