Set up dev environment + fix corrupted math-algebra B1 seed

[EnglandTong]

Summary

Sets up the EduCore development environment for Cursor Cloud agents and fixes a blocking data-corruption bug discovered during setup.

• fix(modules): modules/math-algebra/seeds/B1.json contained a truncated partial duplicate of questions 001–019 spliced in before the complete 25-question array, breaking a string literal with a raw control character. This made JSON.parse fail inside loadModules() — which runs at API startup and in the db:seed* scripts — so the API could not boot at all. Restored the file to the intended valid 25-question array.
• docs: Added AGENTS.md with a ## Cursor Cloud specific instructions section covering services (MongoDB/Redis), how to run the apps, and non-obvious gotchas.

Environment

• Node 22 / pnpm 9.15 (pnpm install).
• MongoDB (mongod binary reused from mongodb-memory-server, installed to /usr/local/bin) and Redis (apt) run as local services; seeded demo accounts via db:seed*.
• Update script: pnpm install (services + system binaries persist in the VM snapshot; AGENTS.md documents how to start them).

Testing

• ✅ pnpm lint
• ✅ pnpm test (after a clean build — see AGENTS.md *.tsbuildinfo gotcha)
• ✅ pnpm build
• ✅ API GET /health → status: ok (mongodb connected, redis ready, 6 modules)
• ✅ API register → login → authenticated /modules
• ✅ Web UI: new student sign-up → authenticated dashboard

educore_register_student_dashboard.mp4

Student dashboard after successful registration

_{To show artifacts inline, enable in settings.}