chore(deps): remove @langchain/openai dependency and simplify test mocks

[earlgreylabs]

Summary

This PR removes the @langchain/openai package from our dependencies, simplifies our unit test mocks, and adds unit test coverage for our local embeddings utility.

Motivation

The @langchain/openai dependency is only used directly in the test suite, as our production codebase relies on local @xenova/transformers for feature extraction.

This PR removes that dependency and simplifies our unit tests by mocking our local src/utils/embeddings.ts utility functions directly, rather than relying on mocking the internals or modules of an external embeddings provider. Additionally, it introduces unit tests for embeddings.ts to restore 100% test coverage for local embeddings utility.

Changes

• package.json:
  • Removed @langchain/openai from dependencies.
• src/docs/store/DocumentStore.test.ts:
  • Removed mocks and imports for OpenAIEmbeddings.
  • Added mock setup for local src/utils/embeddings.ts to isolate unit tests.
• src/utils/embeddings.ts:
  • Added defensive guard check in embedDocuments to handle empty inputs gracefully without invoking the neural-network extractor.
• src/utils/embeddings.test.ts [NEW]:
  • Added unit test suite using vi.hoisted to mock the @xenova/transformers pipeline around top-level awaits.
  • Verified embedDocument and embedDocuments under standard usage, empty inputs, empty arrays, and multi-document queries.

Verification

• npm ls @langchain/openai: no packages
• npm run check: passing (clean formatting, linting, and type-checking)
• npm test: passing (all 86 tests successfully completed)