Review of #172 (finding 1): notes.ReadScoped (brain_read, slice 2) had only outside-brain targets, which os.Root refuses on its own, so a reader bypassing brainfs's Lstat/SameFile stayed green. Adds a static in-brain link, a positive control and an in-brain swap race. Flip: replacing ReadRegularMax with os.OpenRoot().ReadFile turns it red 3/3. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>