Add coding agent self-equip

[danielgaskins]

Summary

• add native repo-scoped Mendmark skills for Codex and Claude Code
• add a portable self-equip protocol for unsupported coding agents
• preserve existing agent policy files and extend clean-wheel assurance

Assurance

• 105 passed, 3 live-profile skips covered by hosted matrices
• 601/601 golden mutations killed by strong evaluators
• enterprise resource budgets passed
• generated skills passed the skill validator
• clean 0.6.1 wheel distribution assurance passed