refactor(routes): load route templates with fs/promises

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/node/plugins/dynamicRoutesPlugin.ts

@@ -1,4 +1,5 @@
 import fs from 'node:fs'
+import { readFile } from 'node:fs/promises'
 import path from 'node:path'
 import c from 'picocolors'
 import pm from 'picomatch'
@@ -148,7 +149,7 @@ export const dynamicRoutesPlugin = async (
 
     load: {
       filter: { id: /\.md$/ },
-      handler(id) {
+      async handler(id) {
         const matched = config.dynamicRoutes.find((r) => r.fullPath === id)
         if (matched) {
           const { route, params, content } = matched
@@ -157,7 +158,7 @@ export const dynamicRoutesPlugin = async (
           moduleGraph.add(id, [routeFile])
           moduleGraph.add(routeFile, [matched.loaderPath])
 
-          let baseContent = fs.readFileSync(routeFile, 'utf8')
+          let baseContent = await readFile(routeFile, 'utf8')
 
           // inject raw content
           // this is intended for integration with CMS