Set up Cursor Cloud dev environment (AGENTS.md)

[DreDre-AI]

Summary

Sets up the development environment for the Rivet monorepo so Cursor Cloud agents can install, lint, test, build, and run the app. Adds an AGENTS.md with a ## Cursor Cloud specific instructions section capturing the non-obvious setup caveats discovered while getting the environment working.

No application code was changed — this only documents the environment. Dependency installation is handled by the startup update script (Node 20 via nvm, Yarn 4.8.1 via corepack, yarn install, yarn unplug tsx).

Key learnings captured in AGENTS.md

• Node 20 required — repo pins node@20.4.0; the VM's default node (Node 22 at /exec-daemon/node) shadows nvm, so Node 20 must be prepended to PATH.
• NPM_TOKEN must be defined (even empty) — .yarnrc.yml references ${NPM_TOKEN} and every yarn command errors if it is unset.
• Yarn 4.8.1 via corepack, then yarn unplug tsx for PnP ESM compatibility.
• Browser/Vite dev mode (yarn workspace @alpic80/rivet-app run start → http://localhost:5173) runs the full node-editor IDE with no Rust/Tauri, ideal for headless cloud. Tauri desktop mode needs Rust + GTK/WebKit libs + a display.

Verification

• yarn test → 62 passed
• yarn lint → 0 errors (pre-existing warnings only)
• Ran the app in browser mode and completed a hello-world: added a Text node, set its value, ran the graph, and the node produced the expected output.

rivet_hello_world_demo.mp4

Text node output after running the graph

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