SIM-4: sim4_breaches has no non-test caller, so the capacity andon is not wired #5775

The SIM-4 contract (contracts/pr-flow-sim4-bounds-v1.yaml, #5774) says each batch is checked against the capacity bounds, but sim4_breaches in crates/aprender-simulate/src/scenarios/pr_flow.rs is called only from tests. Wire it into the batch/andon path (a later batch), then make the contract text match what runs. Found by the batch 4 quorum (quorum/quorum-batch4-sim4-only.json) and the pace seat. Refs #5511.