[sebxt]

The sort in useFrecencySorting compared the stored scores directly. Those scores are only decayed when the same item is visited again, so an item that was used a lot a long time ago kept outranking items used recently, and single visits always tied regardless of when they happened. This contradicts the documented behaviour ("the more recently an item is visited, the higher it will rank").

This change moves the existing decay formula into getDecayedFrecency and uses it in both places: when a visit is recorded (unchanged behaviour) and in the comparator, where both scores are decayed to the same now before being compared. The stored format is unchanged, so existing cached data keeps working.

Tests: added test/useFrecencySorting.test.tsx covering an old visit vs a recent visit with the same score, many old visits vs a few recent ones (driven through visitItem), and frequency still winning when visits are equally recent. The first two fail on main and pass with this change. npm test and npm run lint pass.

Fixes #84

[mathieudutour]

I fixed it directly, the direction of the PR was a bit off (we should be storing a timestamp in the first place)