Use the node id (UUID) instead of an incrementing counter for the unix
control socket name, so each socket identifies its owning node at a glance
(one ubridge per node => node_id is unique). Falls back to the counter only
when no node id is supplied. A single UUID fits sun_path's 107-byte cap
(~69 bytes), so no project_id is needed.
start() now checks whether ubridge exited immediately after launch. An
old ubridge build that does not understand -U exits with a non-zero code
right away; surface the reason from ubridge.log instead of waiting for
connect() to time out 10s later with a confusing "couldn't connect" error.
Add ubridge_control_transport to [Server] config (default "tcp", fully
backward compatible). Selecting "unix" switches the uBridge hypervisor
control channel from the unauthenticated TCP listener (-H) to an AF_UNIX
socket (-U) authenticated in-kernel via SO_PEERCRED.
- UBridgeHypervisor: supports both socket_path (AF_UNIX) and host/port
(TCP); a new `endpoint` property unifies log/error strings for both
- Hypervisor: unix mode allocates a short socket path under a 0700
private runtime dir and unlinks it on stop; tcp mode restores the
original getaddrinfo ephemeral-port allocation
- base_node: reads the transport from config and passes host through
- schemas/config.py + config_samples/gns3_server.conf: new option
Default deployments are unchanged. "unix" requires a ubridge build that
understands -U.
