Add CODEOWNERS file for repository governance

- Grant @core-maintainer team ownership of docs/specification/ and schema/
- Add @auth team as reviewer for authorization-related documentation
- Includes authorization.mdx and security_best_practices.mdx files

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: dsp-ant

.github/CODEOWNERS

@@ -0,0 +1,9 @@
+# CODEOWNERS file for MCP Specification repository
+
+# Global ownership - @core-maintainer team owns docs/specification and schema/ directories
+/docs/specification/ @modelcontextprotocol/core-maintainers
+/schema/ @modelcontextprotocol/core-maintainers
+
+# Authorization-related files - @auth team should be notified
+/docs/specification/**/authorization.mdx @modelcontextprotocol/core-maintainers @modelcontextprotocol/auth
+/docs/specification/**/security_best_practices.mdx @modelcontextprotocol/core-maintainers @modelcontextprotocol/auth