findBreadcrumbPath set node.name='Untitled' in place, mutating the shared
sidebar tree (treeData passed from resolveBreadcrumbNodes). Surface 'Untitled'
via a shallow copy on the returned chain only; input nodes stay untouched.
Add tests for the non-mutation invariant plus applyUpdateOne reducer,
formatRelativeTime buckets, and the pure tree mappers (sortPositionKeys,
pageToTreeNode).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
claude code agent 227
388894c257