stage-7: CLI tool with full subcommands

echo status/doctor/restart/logs/sessions/channel/send commands, symlink at ~/.local/bin/echo. QA fix: discord chat handler tuple unpacking bug. 32 new tests (193 total).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/adapters/discord_bot.py

@@ -4,8 +4,6 @@ import asyncio
 import logging
 import os
 import signal
-from pathlib import Path
-
 import discord
 from discord import app_commands
 
@@ -355,7 +353,7 @@ def create_bot(config: Config) -> discord.Client:
 
         try:
             async with message.channel.typing():
-                response = await asyncio.to_thread(
+                response, _is_cmd = await asyncio.to_thread(
                     route_message, channel_id, user_id, text
                 )