Function compute_view_value 

pub fn compute_view_value(
    def: &ViewDef,
    node: u32,
    props: ColumnsView<'_>,
    topo: &TopologyView<'_>,
    _ids: &IdMap,
    syms: &Interner,
    labels: &[u32],
) -> Option<Value>

Compute the view value for a single node. Returns None when there are no qualifying neighbors for Avg/Min/Max (no sensible neutral value).