React Flow requires parent nodes to appear before their children in
the nodes array. When they don't, it logs "Parent node {id} not
found. Please make sure that parent nodes are in front of their
child nodes in the nodes array" and — more importantly — renders
the child at canvas-absolute coords instead of parent-relative,
flashing it far outside the parent.
topology's buildNodesAndEdges already enforced this at hydrate, but
nestNode + batchNest weren't re-sorting after mutating parentId.
A freshly-nested child often ended up after-first-drag at the
wrong screen position because its new parent sat later in the
array than itself.
Extract sortParentsBeforeChildren() into canvas-topology as a
reusable DFS visit; call it at the tail of both nestNode's set()
and batchNest's commit set(). 923 tests still green — no behaviour
change beyond eliminating the warning and the position flash.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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