* fix(explorer): prevent persisted trees from crashing startup
Persisted expansion restored every directory and recursively flattened the resulting tree during render. Limit automatic restoration to five rendered directory levels and flatten iteratively so deep or broad workspaces cannot exhaust the JavaScript stack.
* fix(explorer): preserve expansion changes during restore
Reconcile completed restoration against the current expansion set atomically so folder interactions made while directory requests are in flight are not overwritten.
* fix(explorer): show hidden files before restoration
* fix(explorer): apply directory toggles atomically
