feat: merge codex openai embedder mock replacement

- Replace openai embedder mock with proper class structure
- Automated code improvement via Codex
- Enhances test mock reliability and consistency
- Resolved merge conflicts in openai-embedder.js

Author: github-actions[bot]

src/mocks/openai-embedder.js

@@ -75,14 +75,6 @@ class OpenAIEmbedder {
   }
 }
 
-// Export default instance for easy use
- OpenAIEmbedder();
-
-
-// Default export
-
-
-
 module.exports = {
   OpenAIEmbedder
-};
+};