[scope:core] Discord→Slack migration COMPLETE (May 2026). All delivery is now...¶

[scope:core] Discord→Slack migration COMPLETE (May 2026). All delivery is now via Slack. Discord channels are DEPRECATED. Delivery format is slack:CHANNEL_ID for Hermes crons and Slack Web API for Prefect flows. Slack channel mapping: hermes-updates=C0B0Y49MMJS, fitness=C0B10621DM4, tech-news=C0B1WG2FJRW, career=C0B0YRA9D61, rugby=C0B0VRZ79C3, agent-ops=C0B15R9MAQL, linear-board=C0B0WPM7C3X.