ns-setup-expo — Expo / EAS platform setup

It is NOT the local Mac toolchain (Xcode, Simulator, CocoaPods → /ns ios local-setup), NOT the everyday run loop (/ns dev → npm run ios/start), and NOT the signing + build itself (/ns ios setup → /ns ios testflight). Those can come before or after; this skill owns Expo account + project wiring + project health.

Detect what's already done, do only the gaps, confirm once before creating the Expo project (it's an outward-facing resource on the user's account).

<platform_context> Every mobile build/release skill must check the OS first. When the OS is Windows or Linux, those skills must load/follow this skill before any iOS TestFlight or Android Play build, because the production build artifact must come from EAS cloud. On macOS, this skill is still needed for EAS project/versioning and can support local EAS builds, but it is not a replacement for Xcode or Android Studio local tooling. </platform_context>

<easprojectid_wiring> The source of truth for the EAS project id is site-config.ts, not app.json. mobile-app/app.config.ts reads extra.eas.projectId = SiteConfig.easProjectId (≈ line 90), and the config is dynamic — so eas init cannot auto-write it.

Flow when easProjectId is still the xxxxxxxx-… placeholder:

1. cd mobile-app && eas init — creates (or links) the EAS project under the logged-in account and prints the project id (a UUID). If it offers to create vs. link an existing one, ask the user which.
2. Write that UUID into site-config.ts → easProjectId: "<uuid>" (replace the placeholder). Do not edit app.config.ts or add it to app.json — app.config.ts already derives it from SiteConfig.
3. Re-verify: cd mobile-app && npx expo config --type public shows extra.eas.projectId as the new UUID. </easprojectid_wiring>