Field id for the “rhs” named child (right-hand side of binary expressions in the expression grammar).
Use with sipha::red::SyntaxNode::field_by_id on a NodeBinaryExpr to get the right operand.
Returns true if name is a valid LeekScript identifier (non-empty, starts with letter or
underscore, rest alphanumeric or underscore). Used e.g. for rename validation in LSP.