docs: add Cursor Cloud dev environment instructions

[RonenMars]

What

Sets up and documents a working development environment for this repo on the Cursor cloud (headless Linux) VM, and records the durable, non-obvious startup/run caveats in AGENTS.md under a new ## Cursor Cloud specific instructions section.

No application code is changed — this PR only adds documentation. Environment setup itself (Node toolchain, dependency install) is handled by the VM update script (npm install) plus a one-time pinned-Node snippet in the agent's ~/.bashrc.

Environment set up & verified

The runnable surface on Linux is the JS toolchain + Expo Web (native iOS/Android builds and Maestro E2E need macOS/Xcode/simulators and are documented as not runnable here).

Task	Command	Result
Install deps	npm ci (startup script uses npm install)	✅ 1268 packages, patch-package applied
Lint	npm run lint	✅ 0 errors (5 warnings, allowed)
Typecheck	npm run typecheck	✅ clean
Unit/integration/i18n tests	npm run test:ci	✅ 153 suites, 1349 passed / 1 skipped
Script tests	npm run test:scripts	✅ 8 suites, 71 passed
Run app (dev)	npx expo start --web --port 8081	✅ bundles (5719 modules), boots

Hello-world (core flow) verified end to end

Started the bundled mock streamer (e2e/mock-server.js) behind a small dev-only CORS proxy, then in the browser completed onboarding → added a server → the live session list populated from the mock streamer (my-project on main/feature/auth/fix/login, other-project on main, with running/waiting/idle statuses). Mock server logs confirm the client hit /api/profiles, /api/sessions, /api/conversations/count, and a session-detail /output fetch.

Expected web-parity limitations (documented in docs/expo-web-support.md, not env bugs): an expo-notifications dev red-box on load and a blank session-detail terminal.

Node

Pinned .nvmrc version (24.15.0) installed via nvm; a guarded snippet in ~/.bashrc makes login/interactive shells prefer it over the sandbox's shadowing node. Node 22.x also meets the repo's stated >= 22.13 minimum.