Event-driven CommandService dispatches exact case-sensitive #command
matches on COMMAND_CHANNEL (default 2) through a single-registration-point
registry; first command #ping -> #pong!. Replies ride COMMAND_CHANNEL:
directed DM back to the sender when present, else broadcast. Failing
handler/send only logs a warn.
DI: CommandModule's factory injects MeshService and attaches itself via
MeshService.attachCommands() — a constructor-level cycle leaves one side
null in NestJS 12's injector (verified), so no forwardRef is used.
Tests 106 -> 121; docs synced (AGENTS.md, MESHTASTIC.md, README).
