Don't read the navigator's exports while it initializes
The redirect boundary imports the navigator, so the navigator can now be
evaluated before app-router-instance. The navigator imports
app-router-instance back, which read `push` and `replace` at module
scope before they were initialized. The public router instance now calls
through to them instead.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
