Merge pull request #1 from ioteverythin/feat/hnsw-streaming-langchain-adapter

fix: remove CONCURRENTLY from HNSW migration

fix: guard langchain-core import + add to CI deps

feat: HNSW index, SSE streaming search, and LangChain ChatMessageHistory adapter

ci: fix workflow to run all tests, not just marked ones

fix(ci): SQLite compat for integration tests

ci: fix all 3 GitHub Actions failures

feat: add test runner script (run_tests.py) -- 314 unit tests pass

docs: add comprehensive usage documentation (6 guides + index)

Initial commit: AgentMemoryDB full application