fix(newos4): the virtual /sys entry leaked into listings, trees and counts (v4.6.88-90)

One phantom entry, three symptoms:
- ls() injected 'sys' whenever it was called without a path, so 'cd _agents; ls' advertised a
  sys directory that does not exist, and list_files('_agents/sys') answered 'Directory not
  found' — the reported false negative. Injection is now gated on dir === root.
- tree() pushed the same virtual name into the walk and dereferenced it, throwing mid-output on
  every root listing. Guarded.
- _gatherFileInfo() walked into /sys and counted a synthetic subtree: 146 files / 114 dirs for a
  44-file / 15-dir store. Virtual entries are skipped.

Verified: root still lists sys; _agents and skills do not; tree('') completes; world model total
(44) equals an independent walk of fs.root (44), agree: true.

0 files changed, 0 insertions, 0 deletions