Function run 

pub async fn run(overrides: CliOverrides) -> ExitCode

Run the Aion workflow server until it shuts down, returning the process exit code.

Initializes the JSON tracing subscriber, loads and validates the merged configuration (file, environment, then overrides), serves the gRPC and HTTP transports, and drains gracefully after the first termination signal. Every failure is logged through tracing and mapped to the exit code contract above; the caller only has to exit with the returned code.