fix: resolve @content alias in Nitro dev SSR worker

- Add @content alias to Nitro config (mirrors Vite resolve.alias)
- Use @content/ alias in loadPageComponent import (works in both
  dev via Nitro alias and build via Vite alias)
- Remove @vite-ignore from dynamic imports
- Add fs.access check before import to prevent crashes

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rsbh

packages/chronicle/src/server/vite-config.ts

@@ -23,6 +23,9 @@ export async function createViteConfig(
       nitro({
         serverDir: path.resolve(packageRoot, 'src/server'),
         ...(preset && { preset }),
+        alias: {
+          '@content': path.resolve(packageRoot, '.content'),
+        },
       }),
       mdx({}, { index: false }),
       react()