:memo: docs: update hero tagline, add media coverage, remove NeurIPS references

- Hero: 'Write Once, Run Anywhere' → 'Compilation for Skills: Capable, Portable, and Securable'
- Badge: ACM CAIS 2026 — AgentSkills'26 Workshop
- Blog: add 小源学AI (May 12, 10 likes/25 saves) and 每日ComputerScience (May 14, 32 likes/23 saves) coverage
- Remove all NeurIPS references per submission policy