Add FolderTree component tests (render, expand, collapse, select,
highlight) and folder filtering tests in noteListHelpers (path
matching, sibling exclusion, archive/trash filtering).
ADR-0033 documents the decision to scan all subdirectories and
expose folder tree navigation, superseding ADR-0006's scanning
constraint.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
