Separate the transport-neutral JSON-RPC connection and server processor from
local process spawning, add websocket support, and document the new API
shape.
Co-authored-by: Codex <noreply@openai.com>
This adds the standalone exec-server stdio JSON-RPC crate and its
smoke tests without wiring it into the CLI or unified-exec yet.
Co-authored-by: Codex <noreply@openai.com>