DetectTunnels runs inside every brain_write and brain_update
(wikiUpkeep -> AutoTunnel). It walked wiki/ with filepath.WalkDir and
opened each note with a blocking os.Open: a FIFO named *.md anywhere
under wiki/ hung the write with no deadline, and a symlinked note's
title became a tunnel candidate (171k leaks in the swap race).
It now walks with brainfs.WalkRegular (regular files only) and reads
titles with readTitleAndCreatedIn (ReadRegular: O_NONBLOCK, handle and
SameFile checks). A wiki/ that is not a real directory yields no
candidates, as filepath.WalkDir did; other walk errors still abort. The
path-based readTitleAndCreated, now unused, is removed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
