proof(flow): item 497 — the strict-lead carry: FlowArm.openNest's ε lead carries trailingPropertyRun = [], accum_step_flow_trace's held-run nested-open disjunct folds into the first

proof(flow): item 497 — the strict-lead carry: FlowArm.openNest's ε lead carries trailingPropertyRun = [], accum_step_flow_trace's held-run nested-open disjunct folds into the first #1165