Show network peers for paired servers

TE
13d ago
+2168-302

Paired servers can inspect their network peers with cmux server pair policy --json. The backend maps the signed policy read to current hosts and original install grants; the CLI checks its protected enrollment and returns only public fields.

Hosted checks pass 16 peer-policy cases and 11 Rust cases on Linux and macOS. The full backend passes 1,048 API cases. This read starts no listener or serving role; live receiving authorization remains a follow-up. Builds on #22388.

Changelog

Added paired-server network peer inspection.