make TSSBOT/start_bot.py a real Discord bot and reuse SREBOT venv (#1227)

- TSSBOT/start_bot.py: replace the print-and-idle stub with a minimal
  discord.py Client (commands.Bot with default+message_content intents).
  Loads TSSBOT/.env via python-dotenv, reads DISCORD_KEY, logs on_ready,
  handles SIGTERM/SIGINT cleanly. Aborts with a clear error if the token
  is missing instead of silently exit-looping.

- TSSBOT/ecosystem.config.js: switch the default interpreter from system
  python3 to SREBOT's venv (../SREBOT/.venv/bin/python). Both bots share
  BOTS/SHARED and the same baseline deps (discord.py, dotenv, …); split
  into a dedicated TSSBOT/.venv only when the dependency sets diverge.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ecosystem.config.js

@@ -4,10 +4,11 @@ require('dotenv').config();
 // you need to point at a different checkout (e.g. local dev).
 const DEPLOY_PATH = process.env.TSSBOT_DEPLOY_PATH || __dirname;
 
-// Default to system python until TSSBOT grows its own dependency set.
-// When BOT/botscript.py lands, create TSSBOT/.venv and switch this to
-// `${DEPLOY_PATH}/.venv/bin/python`.
-const PY_INTERPRETER = process.env.TSSBOT_PY_INTERPRETER || 'python3';
+// Reuse SREBOT's venv by default — both bots share BOTS/SHARED and most
+// runtime deps (discord.py, dotenv, etc.). Split into TSSBOT/.venv once
+// the dep sets diverge meaningfully.
+const PY_INTERPRETER =
+  process.env.TSSBOT_PY_INTERPRETER || `${DEPLOY_PATH}/../SREBOT/.venv/bin/python`;
 
 module.exports = {
   apps: [