Toggle between single-LLM (Claude-only) and multi-LLM (delegate to Gemini, Codex, or other CLIs) modes. Shows current mode, available external CLIs, delegation stats, and logs. Use when the user says "switch to multi", "use Gemini", "delegation status", "how many delegations", or "token savings". Subcommands: `/mode` (status), `/mode multi`, `/mode single`, `/mode stats`, `/mode reset`.
