docs(openspec): add change artifacts for email-loop-prevention
Creates openspec/changes/email-loop-prevention/ with all artifacts:
- proposal.md: Why (MAILER-DAEMON bounce loop incident), what changes
(automated sender detection + message-count cap), capabilities affected
- design.md: Two-layer defence rationale, detection signal table, decisions
on channel/agent boundary split, 20-message cap, one-shot alert, CC-only
routing; risks and trade-offs documented
- specs/email-channel/spec.md: ADDED requirements for detect_automated_message(),
is_automated/automated_reason message dict fields, no-reply guarantee
- specs/registration-notifications/spec.md: ADDED requirements for
notify_loop_escalation() — alert content, one-shot guarantee, CC-only
routing, dev-mode guard
- tasks.md: All 6 sections fully checked (implementation already complete)
https://claude.ai/code/session_01KwvR5hDPjSuJg4kvw5b5e5