Three follow-up review findings from the c2b2e13a review:
1. Rescue heuristic uses pure bbox-non-overlap. The previous
`position.x < 0` branch rescued any child whose parent was
later dragged past it, even when the layout was clearly
recoverable (e.g. relative -40, child still overlaps parent).
New rule: rescue iff the child's bbox has zero overlap with
the parent's bbox — self-calibrating, scales with user-resized
parents, catches screenshot-case and legacy huge-positive data.
2. Toast caps failed-name list at 3 and appends "and N more".
Stops a 50-node partial failure from overflowing the toast
container.
3. Cycle guard on selection-roots walk in batchNest. Corrupt
parentId data can't send the loop infinite now. Cheap
defensive guard — one Set per selected node.
Tests added (923 total, up from 918):
* canvas-topology.test: 4 rescue scenarios — screenshot case
(zero-overlap rescue), negative drift kept, huge-positive
rescued, user-resized layout kept.
* canvas.test: selection-roots filter on a 3-level chain.
* workspace_crud test: PATCH {collapsed:true} runs the UPDATE.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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