Background worker that detects stale messages and takes corrective action: - Auto-fails DMs stuck in "processing" after configurable timeout (default 24h) - Sends system DM reminders for pending messages after ReminderAfter (default 4h) - Escalates unprocessed messages to #approvals channel after EscalateAfter (default 48h) - Deduplicates reminders and escalations to avoid spam - Configurable via SYNAPBUS_STALEMATE_* environment variables Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>