The v1 target combobox in the migration preview now offers only leaf
categories (the inputable end-categories), not intermediate parents, so a
transaction is never mapped to a grouping bucket. Leaves render as a flat,
un-indented list in taxonomy order.
A low-confidence default can still point a v2 category at a non-leaf parent
(e.g. 'Divertissement' #1710); MappingRow re-injects that current target for
its single row via findTaxonomyCategory so the input stays populated, while
new picks remain leaves-only. Adds a findTaxonomyCategory pure helper + tests
(adapter now returns 112 leaves, not the 150-node full tree).
Make the v1 target editable on EVERY row of the categories-migration
preview (StepSimulate), not only the "needs review" ones. Each row now
renders a reused CategoryCombobox (accent-insensitive type-ahead,
keyboard, hierarchical) in place of the read-only text / flat <select>.
A pure adapter (taxonomyToComboboxCategories) flattens the full v1
taxonomy into Category-shaped rows once in StepSimulate and passes it as
a prop to the rows. The full tree (not just leaves) is fed so mid-tree
default targets such as "Divertissement" (id 1710, the default for
"Jeux, Films & Livres") both display and can be re-picked. The target
cell stops click/keydown propagation so picker interaction never toggles
the row preview. Reducer/guard behavior unchanged: resolving a "none"
row still bumps confidence to medium, and the unresolved-count guard
stays functional.
Resolves#246
