Disable Weave routing

When the user invokes $disable-routing, switch the current Codex installation
off the Weave Router without logging out or deleting its router configuration.

1. Explain that the change takes effect on the next codex launch and that it
   can later be reversed with npx --package @weave-os/router -y -- weave-router on --codex{{SCOPE}}.

2. Run exactly:

   npx --package @weave-os/router -y -- weave-router off --codex{{SCOPE}}

3. Report the command result. Do not uninstall the router or alter any other
   Codex settings.