iris-ai
3084491b9b
The first item on the plan landed as two commits on #18. The re-parenting half turned out to be two defects rather than the predicted one -- the old parent's child list erasing a subtree it no longer draws, and the settling walk ordering by a stale depth -- and the `depth()` assertion the note expected to catch it catches only the second. `dirty_size_under` is deleted, so the section that argued for it is marked superseded rather than removed: it says what the bottom-up walk is buying.