Mutation testing found it: changing the right child's `depth + 1` to
`depth + 0` in the depth-first recursion survived the entire suite. The
depth cap was only ever tested against a chain that leans left, so
nothing said whether the right-hand descent counted at all -- a tree
that goes right for a million nodes would have recursed until the
process died, which is precisely what AKSL_TREE_MAX_DEPTH exists to
prevent.
The right-leaning chain is now tested in all three depth-first orders
and breadth-first, which carries its depth on the queue entry instead.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Andrew Kesterson
cc5e7899bb
