The file-path suggestions trie is rebuilt asynchronously and then read by
the suggestions search, which runs on an AsyncHandler worker. It lived in
Model().FilesTrie, so that worker read the (UI-thread-only) model. Move
it to an atomic pointer on the SuggestionsHelper instead: it's the only
place that uses it, the helper is recreated per repo (so the cache still
resets on a repo switch), and an atomic pointer is safe to store from the
build and load from the search worker.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>