Accented memories disappear from search

Replacing picked can discard real Unicode matches because a zero frequency estimate does not mean a token is absent. With two observations titled Αθήνα and two titled salvage, searching missing Αθήνα salvage previously returned the Athens observations. The frequency helper folds Αθήνα to the absent spelling αθηνα, so the new branch replaces the selected terms with salvage. The Athens observations disappear from the results.

Preserve potentially matching Unicode tokens when correcting the selection, while keeping the term and document limits.

Originally posted by @greptile-apps[bot] in thedotmack/claude-mem#4956 (comment)