Move the generic async coroutine out of the host crate into litellm-coroutine,
with its requirements documented in the crate's AGENTS.md. RouteMachine becomes
CallMachine on top of it, host protocol ops move to host/src/protocol.rs, and
the messages, OCR, host-python, python-bridge and legacy callbacks crates adopt
the new types. Adds error definition rules to litellm-rust/AGENTS.md.
Co-authored-by: Yujong Lee <yujong@berri.ai>
core/src/machine was route-neutral runtime code sitting among route surfaces, and the workspace had two modules named machine. It now lives in litellm-host beside the contract it implements, so core only holds routes. The OCR conversion from MachineFault moves to litellm-llms because the orphan rule no longer allows it in core
