Implements a Cisco IOS CLI emulator with four modes (user exec, privileged exec,
global config, interface config), Cisco-style command abbreviation (e.g. sh run,
conf t), enable password flow, and realistic show command output including
running-config, interfaces, IP routes, and VLANs.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
