Add Playwright E2E test suite (25 tests across 4 specs)

- playwright.config.ts: headless CI setup with JSON/HTML reporters
- e2e/global-setup.ts: app reachability check before tests
- e2e/auth.spec.ts: 6 auth tests (sign-in, session, protected routes)
- e2e/compare.spec.ts: 8 API tests (validation, SSE flow, DB persistence)
- e2e/comparisons.spec.ts: 6 CRUD tests (list, detail, 404, view counts)
- e2e/user.spec.ts: 5 user tests (stats, pagination, session binding)
- e2e/helpers.ts: shared SSE parsing, auth, URL resolution utilities
- e2e/README.md: setup and run instructions
- AGENTS.md: updated with LLM provider notes and testing docs
- .gitignore: added playwright report/result directories
- package.json: added @playwright/test and test:e2e scripts

AGENTS.md

@@ -3,3 +3,59 @@
 
 This version has breaking changes — APIs, conventions, and file structure may all differ from your training data. Read the relevant guide in `node_modules/next/dist/docs/` before writing any code. Heed deprecation notices.
 <!-- END:nextjs-agent-rules -->
+
+# Comparaison — Project Agent Rules
+
+## LLM Provider
+
+- **Base URL**: `https://nano-gpt.com/api/v1` (not `api.nano-gpt.com`)
+- **API Key**: Use `NANOGPT_API_KEY` env var from the host's Docker `.env`
+- **Model**: `minimax/minimax-m2.7` (supports `response_format: {type: json_object}`)
+- **Schema tolerance**: The LLM output may deviate from the requested schema. The provider code (`src/lib/llm/providers/openai.ts`) includes `normalizeResult()` to handle common deviations (overallScore as object, sources as strings, dimensions as array of objects). Do NOT assume the LLM returns the exact schema.
+
+## Development
+
+```bash
+# Local dev
+npm run dev
+
+# Build Docker image
+docker compose build
+
+# Run container
+docker compose up -d
+
+# Run E2E tests
+npm install
+npm run test:e2e:install
+npm run test:e2e
+```
+
+## Deployment
+
+Deployed to `ubuntu:/srv/compose/comparaison/` via `docker compose`.
+Traefik routes `comparaison.local.tophermayor.com` → container port 3000.
+
+## Environment Variables
+
+Required in `.env`:
+- `DATABASE_URL` — PostgreSQL connection string
+- `BETTER_AUTH_SECRET` — Session secret (min 32 chars)
+- `BETTER_AUTH_URL` — Auth callback URL
+- `LLM_API_KEY` — NanoGPT API key (Hermes `NANOGPT_API_KEY` works)
+- `LLM_BASE_URL` — `https://nano-gpt.com/api/v1`
+- `LLM_MODEL` — `minimax/minimax-m2.7`
+
+## Key Routes
+
+| Route | Method | Auth | Description |
+|-------|--------|------|-------------|
+| `/api/compare` | POST | Yes | Start SSE comparison stream |
+| `/api/comparisons/[slug]` | GET | Yes | Get comparison by slug |
+| `/api/user/comparisons` | GET | Yes | List user's comparisons |
+| `/api/user/stats` | GET | Yes | User statistics |
+| `/api/auth/sign-in/email` | POST | No | Email/password sign-in |
+
+## Testing
+
+E2E tests live in `e2e/` and use Playwright. See `e2e/README.md` for setup.