Cover the network-facing CLI command modules with unit tests:

- tests/unit/commands/test_netbox.py: extend the existing exit-code
  tests with the Sync error-classification helpers
  (_check_netbox_instance, _check_netbox_connectivity), table building
  (_build_netbox_table), the --list/--check/--no-wait/--filter paths
  of Sync.take_action, argument assembly in Ironic and Manage,
  Versions, the nbcli bootstrap and argument quoting in Console, and
  the device lookup fallback chain and report formatting in Dump.
- tests/unit/commands/test_sonic.py: SonicCommandBase helpers (device
  lookup, config context filtering, SSH connection details, backup
  filename probing, the exec-command helpers) and the take_action
  control flow of Load, Backup, Ztp, Reload, Reboot, Reset, Show,
  Console, and Dump.
- tests/unit/commands/test_sonic_validate.py: source collection and
  config acquisition of Validate (_collect_sources,
  _configs_from_export_dir, _config_from_netbox,
  _config_from_generate), its exit-code contract and report
  formatting, and the provision-state derivation and sorting of List.

Assisted-by: Claude:claude-fable-5
Signed-off-by: Christian Berendt <berendt@osism.tech>