Fixed parent() to handle nodes at the right edge of non-full trees
by walking through virtual parent nodes until finding one within
the tree's node count range. This prevents out-of-range crashes
for trees with non-power-of-2 leaf counts.
MlsGroupTest.testEpochAdvancesOnCommit still fails because the
MlsGroup commit logic needs to be updated for the corrected tree
topology (root/directPath now correctly handle non-power-of-2 trees).
This is a known regression that requires deeper refactoring of the
group commit/processCommit code paths.
Test results: 40/41 interop passing (98%), 1 MlsGroupTest regression.
https://claude.ai/code/session_01NocQDWj2Y92FugjfgazzL3
Claude
9d910b0bed