feat: Discord-based agent wakeup replacing spawn

New wakeup flow:
1. Create private Discord channel for the agent
2. Send wakeup message with slot context + workflow reference
3. If Dirigent detected (globalThis.__dirigent), create work-type channel
4. Fallback to api.spawn if Discord not configured

New config fields: discordBotToken, discordGuildId
New file: plugin/calendar/discord-wakeup.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugin/calendar/index.ts

@@ -32,3 +32,4 @@ export * from './types';
 export * from './calendar-bridge';
 export * from './scheduler';
 export * from './schedule-cache';
+export * from './discord-wakeup';