I dug through the installed Claude Code binary. Short version: it is an embedded JS VM runtime inside Claude Code, not a separate node workflow.js process.
Installed version here:
claude 2.1.183
/Users/joshbeckman/.local/state/tec/toolchain/base_profile/bin/claude
→ /nix/store/l6xql5ywjbm0ppsjwpf740clkdbw3mw8-claude-code-2.1.183/bin/.claude-wrapped