docs(readme): add 3-step guide to fork the Space and wire OpenRouter

- New "Run your own copy on a Hugging Face Space" section: duplicate the
Space, grab an OpenRouter key, paste it as a Space secret
- Fix the stale OPENAI_API_KEY hint in the local-dev snippet (we use
OPENROUTER_API_KEY)

Made-with: Cursor

README.md

@@ -93,7 +93,7 @@ Backend and frontend run as two separate processes in dev (Vite proxies `/api`,
 ```bash
 # terminal 1 — backend (Express + Hocuspocus on :8080)
 cd backend
-cp .env.example .env          # fill in HF_TOKEN, OPENAI_API_KEY, ...
+cp .env.example .env          # fill in OPENROUTER_API_KEY, OAUTH_*, HF_TOKEN, ...
 npm install
 npm run dev
 
@@ -116,6 +116,16 @@ docker run -p 8080:8080 --env-file backend/.env collab-editor
 
 Then open http://localhost:8080.
 
+### Run your own copy on a Hugging Face Space
+
+Want your own editor with your own AI key? Three steps:
+
+1. **Duplicate the Space.** On https://huggingface.co/spaces/tfrere/research-article-template-editor, click `⋯ → Duplicate this Space`. Pick your namespace and visibility. HF copies the Dockerfile, the OAuth wiring and rebuilds the image automatically.
+2. **Get an OpenRouter API key.** Sign up at https://openrouter.ai and create a key under https://openrouter.ai/keys. The chat agent and the embed studio call OpenRouter through the [Vercel AI SDK](https://ai-sdk.dev/), so any model exposed by OpenRouter works (defaults to `anthropic/claude-sonnet-4`).
+3. **Add the key as a Space secret.** In your duplicated Space, go to `Settings → Variables and secrets → New secret`, name it `OPENROUTER_API_KEY` and paste the value. Optional: add `OPENROUTER_MODEL` as a public variable to override the default model. Save - the Space restarts and the AI features light up.
+
+That's it. The HF OAuth app, the persistence dataset (`<your-space>-data`) and the Docker build are wired automatically by HF Spaces; you only need the OpenRouter key to unlock the AI side.
+
 ## Scripts
 
 ### Backend (`cd backend`)