Document the operational patterns established while adding CT100 and
CT101 as peers via Docker, plus incidental fixes:
- Docker compose template for headless peer containers
- One-off setup key naming convention and API creation
- Peer rename via API PUT (works, unlike setup keys)
- Mac daemon kickstart via 'sudo launchctl kickstart -k system/netbird'
(service name is 'netbird', not 'io.netbird.client')
- UPNP auto-port-mapping discovery in NetBird client
- CT100 PermitRootLogin drop-in override (first-match-wins sshd quirk)
