Comprehensive test coverage for the semantic memory module:
- _simple_hash_embedding determinism and normalization
- cosine_similarity including zero vectors
- SemanticMemory: init, index_file, index_vault, search, stats
- _split_into_chunks with various sizes
- memory_search, memory_read, memory_write, memory_forget tools
- MemorySearcher class
- Edge cases: empty DB, unicode, very long text, special chars
- All tests use tmp_path for isolation, no sentence-transformers needed
86 tests, all passing. 1393 total tests passing.