Function partition_on_stack 

pub fn partition_on_stack(
    source: &str,
    stack: &StackTarget,
    hop_cost_pitches: f64,
) -> StackPartition

Partition source onto a STACK: region compilation against the stack’s analog tier, 3D placement, the exact-ℚ thermal solve, and the cooling gate — in that order, each failure a named ledger entry. Deterministic end to end.