Always provide virtual module

Author: markdalgleish

packages/react-router-dev/vite/rsc/plugin.ts

@@ -505,11 +505,6 @@ export function reactRouterRSCVitePlugin(): Vite.PluginOption[] {
         }
       },
       load(id) {
-        // react-router-serve is not used in dev mode
-        if (viteCommand !== "build") {
-          return `export default {};`;
-        }
-
         if (id === virtual.reactRouterServeConfig.resolvedId) {
           const rscOutDir = resolvedViteConfig.environments.rsc?.build?.outDir;
           invariant(rscOutDir, "RSC build directory config not found");