Fix CLI arg parsing to allow usage with no arguments (#12925)

.changeset/fast-olives-invent.md

@@ -0,0 +1,5 @@
+---
+"@react-router/dev": patch
+---
+
+Fix CLI parsing to allow argumentless `npx react-router` usage

packages/react-router-dev/bin.js

@@ -5,8 +5,8 @@ let arg = require("arg");
 // default `NODE_ENV` so React loads the proper version in it's CJS entry script.
 // We have to do this before importing `run.ts` since that is what imports
 // `react` (indirectly via `react-router`)
-let args = arg({}, { argv: process.argv.slice(2), stopAtPositional: true });
-if (args._[0] === "dev") {
+let args = arg({}, { argv: process.argv.slice(2), permissive: true });
+if (args._.length === 0 || args._[0] === "dev") {
   process.env.NODE_ENV = process.env.NODE_ENV ?? "development";
 } else {
   process.env.NODE_ENV = process.env.NODE_ENV ?? "production";