feat(memory): add three-layer memory system with embedders and vector stores

- 3 memory layers (Conversation History, Semantic Recall, Working Memory)
- 6 embedders (OpenAI, Vertex, Ollama, Bedrock, Mistral, Cohere)
- 5 vector stores (In-Memory, Redis, Qdrant, PGVector, Pinecone)
- MemoryCoordinator for unified memory access
- Memory processors for context management
- CLI memory commands (list, stats, search, clear, export, import)
- SDK methods: createThreeLayerMemory, getWorkingMemory, updateWorkingMemory,
  getThreeLayerMemoryStats, searchMemory, storeConversation
- Continuous test suite: 46/46 tests passing (7 skipped - optional API keys),
  including E2E tests for generate()/stream() SDK and CLI with memory

Author: murdore