Implement `describe_balanced_nodes(values)` for a binary tree represented as a zero-based heap array. For an existing node at index `i`, its children are at `2*i + 1` and `2*i + 2`. A `null` slot means no node; a valid input never places an existing node below a missing parent. A node's subtree is height-balanced when both child subtrees are height-balanced and their heights differ by at most one. The empty subtree has height `0` and a leaf has height `1`. Return one integer record `[index, level, balanced_flag]` for every existing node, ordered by increasing array index. The root is at level `0`. Encode a balanced subtree as `1` and an unbalanced subtree as `0`, so the return type is a portable list of integer lists. ### Constraints - `0 <= len(values) <= 200000` - Every non-null value is an integer in `[-10^9, 10^9]`. - Values need not be unique; use the array index as node identity. - An empty input returns an empty list. ```hint Stress irregular shapes Test a one-sided chain, a root with only one child, and missing children at different levels. ``` ```hint Check depth robustness The largest valid input should not fail solely because the tree is deep. ```