Function with_runtime_flags 

pub(crate) fn with_runtime_flags(
    meta: &HashMap<String, Value>,
    args: Vec<String>,
) -> Vec<String>

args as stored in cmd:args, plus any runtime flag it lacks, taken from the pane’s agent:runtime (or the defaults when it has none).

Never overrides a flag already present: the frontend’s rebuild and seed_launch put them there, and a definition’s own --model is the agent’s choice. Leaves alone a provider the menu does not wire, an unknown provider, and an empty argv (nothing to extend). Idempotent.