docs(readme): add Raven ecosystem entry

[cyfyifanchen]

What changed

• Added Raven to the EverMind Ecosystems table in the English README.
• Added the matching Raven entry to the Chinese README.
• Synced the ecosystem description with the Raven README by including AI-native interfaces.

Why

EverOS should point readers to the current Raven repository and use the same ecosystem positioning Raven uses for the self-improving agent harness.

Impact

Documentation-only change. No runtime behavior is affected.

Validation

• git diff --check HEAD~1..HEAD
• Verified the Raven links and descriptions are present in both README files with rg.