- Install ALL skills to temp HOME (not just one) to catch missing SKILL.md
- Pre-flight asserts every .agents/ dir has both SKILL.md and openai.yaml
- Assert no "invalid SKILL.md" or "Skipped loading" in stderr
- Add existingHome option to runCodexSkill for pre-populated temp HOMEs
- Increase discover test timeout to 120s (all-skills load takes longer)