stat() follows links, so `stat.type == link` was always false: every
FileEntry reported isSymlink=false and walkFiles happily descended
symlinked directories — an escape hatch out of the workspace and a
cycle risk for the search engine built on the walk. The lister already
runs with followLinks: false, so the Link entity itself is the signal.
listDir keeps reporting the target type for the UI; walkFiles skips
descent into symlinked dirs and still emits file symlinks as entries.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>