Function recompute_pane 

pub fn recompute_pane(
    pane: &PaneCellsInputs,
    state: &mut VirtualRowsWorkerState,
    providers: &VirtualRowProviderRegistry,
) -> WorkerDecision

D.4.d.2.1.c (2026-05-30): per-pane recompute. Same shape as cells_worker::recompute_pane. Visible for tests that want to assert per-pane decisions without driving the aggregate.

Writes via pane.virtual_rows_matrix (the per-buffer registry cell), so two panes showing the same buffer share a single output cell — the second pane sees a CacheHit against the rebuild the first one already published (same (buffer_id, providers, source_line_count) fingerprint).