langchain

dfafaa98 - feat(agents): Option B — _BackendProtocol in langchain, backend on AgentRuntime

feat(agents): Option B — _BackendProtocol in langchain, backend on AgentRuntime - _BackendProtocol: private Protocol with core backend methods (read/write/ls etc.) - AgentRuntime.backend: _BackendProtocol | None — typed at the langchain layer - create_agent accepts backend= and threads it into AgentRuntime at dispatch time - No AgentRuntime subclass or BackendMiddleware needed in subpackages