fix: handle empty workspace folders array to prevent path type errors

- Replace .at(0) with safe array access using length checks
- Fixes "path argument must be of type string" error when workspace is empty
- Addresses regression introduced between v3.25.17 and v3.26.7

Fixes #7695

src/services/mcp/McpHub.ts

@@ -86,7 +86,10 @@ const createServerTypeSchema = () => {
 			type: z.enum(["stdio"]).optional(),
 			command: z.string().min(1, "Command cannot be empty"),
 			args: z.array(z.string()).optional(),
-			cwd: z.string().default(() => vscode.workspace.workspaceFolders?.at(0)?.uri.fsPath ?? process.cwd()),
+			cwd: z.string().default(() => {
+				const workspaceFolders = vscode.workspace.workspaceFolders
+				return workspaceFolders && workspaceFolders.length > 0 ? workspaceFolders[0].uri.fsPath : process.cwd()
+			}),
 			env: z.record(z.string()).optional(),
 			// Ensure no SSE fields are present
 			url: z.undefined().optional(),