syncular-command — one JSON command surface over the Rust client core

The command router the conformance shim proved (JSON in, JSON out, bytes as {"$bytes": hex}) factored into a transport-agnostic module so BOTH the stdio conformance shim AND the FFI native core dispatch through the same code. That keeps a single command surface, conformance-locked via the shim: whatever the shim exercises, the FFI core inherits.

The router is generic over the Transport seam. The shim binds it to a stdio host (transport inverted to the harness); the FFI crate binds it to a real native HTTP+WS transport. Everything host-specific — realtime notification draining, deferred requests, event queues — stays in each host; only the pure method → result dispatch (and its JSON parsing) is shared here.