CHANGELOG (Added: the "Check hierarchy" window; Fixed: the parent checks
at save time and the budget rows of a category whose parent is deleted or
gone), the Categories section of the user guide and its docs.* keys in
both languages, and docs/architecture.md: the categoryHierarchy module, the
diagnostic, the validation and its typed error, the window, the budget
root rule, and what stays out of scope (drag-and-drop, archive restore).
Resolves#393
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
03e32afc02