Claude Code runs hooks via a non-interactive /bin/sh. On setups where node
isn't on that shell's PATH (Nix/nix-darwin, nvm, fnm), every prompt errored
with "/bin/sh: node: command not found". Guard each hook command so it runs
node only when present and exits 0 otherwise, no more per-prompt noise. The
slash-command skills are unaffected; only the always-on activation needs node.
Document the requirement in the README install section.
Closes#51.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>