#765 Telegram connector + real-time triggers on the reusable reaction framework

Second channel, validated e2e. Net-new only: TelegramApp (enterprise/apps/pre_installed/telegram.py, send_message via Bot API + bot_token secret), CHANNEL_TOOLS['telegram'], and the ingestion adapter (api/oauth_handlers/telegram_int.py: connect = getMe validate -> store token in Vault tenants/{t}/telegram -> install app -> setWebhook with per-tenant secret_token; webhook /api/v1/triggers/telegram resolves tenant by X-Telegram-Bot-Api-Secret-Token header -> normalize {sender,body,reply_to=chat_id} -> dispatch_reaction). Reused unchanged: inbound_rules, match_rule, reaction_agent, submit_workflow. reactions.py added generic reply_to (chat_id for telegram, email for gmail). agent_catalog telegram_send. MCP connect_telegram/watch_telegram/stop_telegram_watch. Validated: message to @highway_agent_bot -> webhook -> Reaction dispatched (channel=telegram) -> TelegramApp.send_message -> 200, joke reply ~14s. telegram_integrations migration. Bot token was pasted in chat (rotate if transcript shared).