Function resolve_page_reference_fixpoint 

pub fn resolve_page_reference_fixpoint<T>(
    document: &mut Document,
    layout: impl FnMut(&Document) -> (BTreeMap<String, u32>, T),
    max_iterations: u32,
) -> (PageFixpointOutcome, T)

Drive page-reference resolution to a fixpoint against an injected layout.

layout lays document out and returns its label→page map plus the full layout artifact T, so the caller keeps the final artifact without an extra pass. Each round resolves page references from the previous map, then re-lays-out; it converges when the map stops changing. Oscillation (a previously-seen map recurs) and exhausting max_iterations both yield NotConverged with the most recent artifact.

Layout is a parameter rather than a direct call so mos-eval does not depend on mos-layout and the convergence logic can be tested with a mock.