Owner Pivot

OWNER plane — PIVOT-SOLVE (Jay, 2026-06-15): from any flow, "solve for any other piece" by re-clamping a section/variable as the new target. This is the existing re-clamp made callable, NOT a new solver: via="expand" → expand.expand(object, {target: to_value}) — re-clamp a Result delta (DV) to a value and re-solve the rest (the per-instance pivot). via="execute" → execution.execute(target) — clamp a DIFFERENT output object as the goal and re-solve its method. Honest about reach: a target the operators can't serve comes back matched:[]/unmatched (expand) or resolved:false (execute) — never a fabricated solve. Wraps the additive operators only; does NOT touch reduce/solve.