Add 10 new MST tests: get from empty tree, delete nonexistent key, remove all keys produces empty tree CID, update existing key, order independence (50 keys in 3 orderings), 100-key stress test, keyHeight edge cases. One test (insert-then-remove-every-other) is skipped because it exposes an integer overflow bug in MST tree rebalancing after deletions — the tree.get() call panics after removing keys. This needs investigation in the delete/rebalance path. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>