Add e2e tests for embeddings.generate() method

[mattapperson]

Summary

This PR adds comprehensive end-to-end tests for the newly added embeddings API functionality.

Changes

• ✅ Added tests/e2e/embeddings.test.ts with 5 test cases covering:

  • Single text input embeddings generation
  • Multiple text inputs (batch processing)
  • Embedding dimensions consistency validation
  • Edge case handling (empty strings)
  • Model information validation
  • Support for both array and base64 encoded embeddings

• ✅ Updated tests/e2e/README.md to document the new test suite

Test Results

All 5 tests pass successfully:

✓ should successfully generate embeddings for a single text input
✓ should generate embeddings for multiple text inputs
✓ should generate consistent embedding dimensions
✓ should handle empty string input gracefully
✓ should include model information in response

Model Used

Tests use openai/text-embedding-3-small model via OpenRouter's embeddings API.

Test plan

• All tests pass locally
• Tests properly handle both array and base64 response formats
• Documentation updated