v0.1.6

Guided setup and productization release.\n\nHighlights:\n- add a guided setup flow with setup-runtime.mjs guided-setup\n- polish doctor diagnostics with placeholder, callback, and Tailscale readiness checks\n- add first-run success transcript/screenshot artifacts\n- rewrite the README and setup flow around a canonical low-friction install -> setup -> done path\n\nWhat this improves:\n- faster first-run setup\n- clearer Shopify app values\n- clearer post-install validation\n- better adoption-facing documentation\n\nKnown limits:\n- Shopify app creation, credential entry, OAuth approval, and HTTPS ingress still require operator action\n- the skill remains intentionally narrow and security-first\n