docs: update codex doc URL (#987)

Refs #967
Closes #968

Author: OrKoN

README.md

@@ -150,7 +150,7 @@ Restart Claude Code to have the MCP server and skills load (check with `/skills`
 
 <details>
   <summary>Codex</summary>
-  Follow the <a href="https://github.com/openai/codex/blob/main/docs/advanced.md#model-context-protocol-mcp">configure MCP guide</a>
+  Follow the <a href="https://developers.openai.com/codex/mcp/#configure-with-the-cli">configure MCP guide</a>
   using the standard config from above. You can also install the Chrome DevTools MCP server using the Codex CLI:
 
 ```bash