test: add Qdrant adapter tests

[OMSHIVSHARAN]

Summary

Adds tests for the Qdrant vector database adapter.

Changes

• Add tests for instrumentQdrantClient
• Cover search and emitted vector_op query events
• Cover upsert and emitted vector_op events
• Cover delete and emitted vector_op events
• Verify return values are passed through correctly

Testing

• pnpm --filter @obyflow/adapter-vectordb test
• 5 test files passed
• 12 tests passed
• No regressions

Related Issue

Part of #68

[AnupamKumar-1]

LGTM, thanks @OMSHIVSHARAN! Pulled the branch and ran it locally: the 3 new Qdrant tests pass, and the build and lint are clean. It follows the pinecone.test.ts template and covers search, upsert and delete, plus the return-value passthrough.

Note: this only covers Qdrant. #68 also lists chroma.ts, milvus.ts and weaviate.ts, which still have no tests. I've changed the PR description to "Part of #68" so the issue stays open until those are done. Happy for them to come as separate PRs.