Function derive_runs 

pub fn derive_runs(
    clock: &impl Clock,
    task_id: TaskId,
    run_policy: &RunPolicy,
    already_derived: u32,
    schedule_origin: u64,
) -> DerivationResult

Derives runs from a task run policy.

This function is the policy-routing boundary for run derivation. Concrete policy behavior is implemented in policy-specific modules.

schedule_origin is the stable base timestamp used by repeat policies to compute deterministic scheduled times.