channels.nixos.org answers <branch>/git-revision with a redirect, which
router-upgrade check did not follow: on a real router it saw an empty
answer. The test channel is now an HTTP server that redirects the same way.
The page labelled the running release "stable", but nixos-unstable already
calls itself the next release (26.11 does not exist as a branch yet). It
offers none, unstable and the stable releases listed in the code (26.05).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F