fix: use separate environment variable for root path in mock update server

Author: nmggithub

scripts/mock-update-server.ts

@@ -4,7 +4,7 @@ import { fileURLToPath } from "node:url";
 
 const port = Number(process.env.T3CODE_DESKTOP_MOCK_UPDATE_SERVER_PORT ?? 3000);
 const root =
-  process.env.T3CODE_DESKTOP_MOCK_UPDATE_SERVER_PORT ??
+  process.env.T3CODE_DESKTOP_MOCK_UPDATE_SERVER_ROOT ??
   resolve(dirname(fileURLToPath(import.meta.url)), "..", "release-mock");
 
 const mockServerLog = (level: "info" | "warn" | "error" = "info", message: string) => {