Add GitHub Copilot appendix to primitives matrix

[cobusgreyling]

Goal

Document how GitHub Copilot (Coding Agent, CLI, or workspace agent) maps to loop primitives.

Files

• docs/primitives-matrix.md
• examples/README.md (tool directory row)

Acceptance criteria

• New ## Appendix: GitHub Copilot section
• Map Automations/Scheduling, Skills, State, Worktrees, and verification split
• Note Copilot-specific constraints (sandbox, PR-only writes, human merge gate)
• Week-one Daily Triage example — report-only, state updates only

Estimated time: ~30 minutes

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