Add Devin appendix to primitives matrix

[cobusgreyling]

Goal

Add a Devin (Cognition) appendix mapping loop primitives to Devin's sessions, playbooks, and connectors.

Files

• docs/primitives-matrix.md

Acceptance criteria

• New ## Appendix: Devin section
• Map scheduling (sessions vs cron), skills/playbooks, state files, PR-only writes
• Week-one Daily Triage — report-only, no repo writes beyond STATE.md
• Human gate callouts for L2+ (Devin PRs still need review)

Estimated time: ~30 minutes

Comment "I'll take this" to get assigned.