Function insert_children 

pub fn insert_children(
    text: &str,
    parent: &NodeId,
    children: &[NewChild],
) -> Result<String, AxError>

Hangs new children under a node, returning the whole text.

The children land directly below the node’s last descendant, so the table stays in reading order and the numbers a person saw yesterday still point at the same work. New ordinals continue after the node’s existing children rather than reusing a gap: a plan index is a name, and reusing one would silently move somebody’s evidence.

Errors

Refuses a table that does not parse, an index no row carries, an empty list of children, a child whose text is blank, a weight of zero (a node worth nothing is a row nobody will ever be given), and a split that would push the plan past plan::NODE_DEPTH_MAX.