Replace lexicographic sort with numeric (major, minor, patch) sort
across all 7 version-directory sort sites in find_node_bin_dir.
Lexicographic sort incorrectly orders v20.9 > v20.11 (because '9' > '1')
which could select an older Node.js version and cause agent preflight
failures for version-gated agents like OpenClaw (requires >=22.12.0).