Function prepare_agent_command 

pub async fn prepare_agent_command(
    agent: &RegistryAgent,
    user_args: &[String],
) -> Result<PreparedCommand>

Builds a PreparedCommand from a registry entry and extra user arguments.

The runtime first attempts to download and extract a binary distribution for the current platform, then falls back to npx or uvx package runners if no binary target exists. Any resolved temporary directory is returned so callers can keep it alive while the spawned process runs.