fix: force $app/* modules to be bundled (#13977)

* fix: force `$app/*` modules to be bundled

* use a string

* OCD

Author: Rich-Harris

.changeset/flat-eggs-start.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: force `$app/*` modules to be bundled

packages/kit/src/exports/vite/index.js

@@ -297,7 +297,12 @@ async function kit({ svelte_config }) {
 						// that bundle later on from resolving the export conditions incorrectly
 						// and for example include browser-only code in the server output
 						// because they for example use esbuild.build with `platform: 'browser'`
-						'esm-env'
+						'esm-env',
+						// This forces `$app/*` modules to be bundled, since they depend on
+						// virtual modules like `__sveltekit/paths` (this isn't a valid bare
+						// import, but it works with vite-node's externalization logic, which
+						// uses basic concatenation)
+						'@sveltejs/kit/src/runtime'
 					]
 				}
 			};