Audit type coverage & DX in integration tests

[namuol]

Given that integration tests don't need rebuilds to test, they're the fastest way to evaluate APIs for type correctness and general DX:

• langchain/src/agents/tests/agent.int.test.ts
• langchain/src/agents/tests/zapier_toolkit.int.test.ts
• langchain/src/callbacks/tests/langchain_tracer.int.test.ts
• langchain/src/chains/question_answering/tests/load.int.test.ts
  • loadQAStuffChain
  • loadQAMapReduceChain
  • loadQARefineChain
• langchain/src/chains/summarization/tests/load.int.test.ts
• langchain/src/chains/tests/chat_vector_db_qa_chain.int.test.ts
• langchain/src/chains/tests/combine_docs_chain.int.test.ts
• langchain/src/chains/tests/llm_chain.int.test.ts
• langchain/src/chains/tests/sql_db_chain.int.test.ts
• langchain/src/chains/tests/vector_db_qa_chain.int.test.ts
• langchain/src/chat_models/tests/chatanthropic.int.test.ts
• langchain/src/chat_models/tests/chatopenai.int.test.ts
• langchain/src/document_loaders/tests/college_confidential.int.test.ts
• langchain/src/document_loaders/tests/github.int.test.ts
• langchain/src/document_loaders/tests/hn.int.test.ts
• langchain/src/document_loaders/tests/playwright_web.int.test.ts
• langchain/src/document_loaders/tests/puppeteer.int.test.ts
• langchain/src/embeddings/tests/cohere.int.test.ts
• langchain/src/embeddings/tests/openai.int.test.ts
• langchain/src/llms/tests/cohere.int.test.ts
• langchain/src/llms/tests/huggingface_hub.int.test.ts
• langchain/src/llms/tests/openai-chat.int.test.ts
• langchain/src/llms/tests/openai.int.test.ts
• langchain/src/llms/tests/replicate.int.test.ts
• langchain/src/memory/tests/summary.int.test.ts
• langchain/src/prompts/tests/load.int.test.ts
• langchain/src/retrievers/tests/metal.int.test.ts
• langchain/src/retrievers/tests/supabase.int.test.ts
• langchain/src/tests/sql_database.int.test.ts
• langchain/src/tools/tests/webbrowser.int.test.ts
• langchain/src/vectorstores/tests/hnswlib.int.test.ts
• langchain/src/vectorstores/tests/memory.int.test.ts
• langchain/src/vectorstores/tests/milvus.int.test.ts
• langchain/src/vectorstores/tests/mongo.int.test.ts
• langchain/src/vectorstores/tests/opensearch.int.test.ts
• langchain/src/vectorstores/tests/pinecone.int.test.ts
• langchain/src/vectorstores/tests/supabase.int.test.ts
• langchain/src/vectorstores/tests/weaviate.int.test.ts
• test-exports-cf/src/index.int.test.ts