Function execute_plan 

pub async fn execute_plan(
    observation: &Observation,
    target_key: &str,
    plan: &PlanKind,
    permit: &ExecutionPermit,
    config: &LoopConfig,
) -> Result<ActionOutcome, PilotError>

Executes a verification plan under an issued execution permit.

Dispatches to the appropriate oracle or paired-patch path based on the plan variant. Returns an error if the permit scope does not match target_key.