Function run_with_respawn 

async fn run_with_respawn(
    state: &Arc<ServerState>,
    tool: &str,
    selector: &str,
    method: &str,
    params: Value,
) -> Result<(Value, AddressCanonicalizer), ErrorEnvelope>

Acquire the worker mutex and run the RPC. On a transport crash, respawn OUTSIDE the lock (R3 seat-G) and retry once; a second crash on the same request poisons the selector (§4.3). Attach state commits atomically under the lock (R2 seat-C).