Adds a Guard that resolves every path against an allowlist of absolute
roots (default: cwd) and rejects anything escaping via relative segments,
absolute paths outside the root, or symlinks (including symlinked
parents on writes).
Closes audit finding C1: fs.read/fs.write/fs.edit/fs.glob/fs.grep/fs.ls
previously accepted any absolute path; the only protection was a
substring denylist (.env, .ssh/, ...) which missed /etc/shadow, kube
configs, IDE secrets, and anything reachable via symlink.
