docs: clean up VM backend setup instructions

openhands/usage/agent-canvas/backend-setup/vm.mdx

@@ -23,10 +23,12 @@
 
 ## 2. Install Prerequisites
 
-On Ubuntu:
+You need **Node.js 22.x** and **uv**. See the [Agent Canvas quickstart](https://github.com/OpenHands/agent-canvas#quickstart) for all install options.
+
+On Ubuntu the shortest path is:
 
 ```bash
-apt-get update && apt-get install -y curl git
+sudo apt-get update && sudo apt-get install -y curl
 
 # Node.js 22.x (via nvm, asdf, or NodeSource)
 # uv (for the agent server runtime):
@@ -61,7 +63,7 @@
 1. Click the backend switcher → **Manage Backends** → **Add Backend**.
 2. Fill in:
    - **Name** — e.g. `my-vm`
    - **Host / Base URL** — `http://localhost:8000` (if using an SSH tunnel) or the VM's URL if you've set up a reverse proxy
    - **API Key** — the `LOCAL_BACKEND_API_KEY` from step 3
 3. Save and select it as the active backend.
 
@@ -75,9 +77,9 @@
 
 Then use `http://localhost:8000` as the backend URL.
 
 ## 5. (Optional) Add a Domain with nginx + TLS
 
 If you want direct HTTPS access without an SSH tunnel, point a domain at the machine and front it with nginx + Let's Encrypt.
 
 ### Point a Domain at the Machine
 
@@ -91,16 +93,16 @@
 
 Update your network firewall to additionally allow:
 
 - **Port 80 (HTTP)** — open to `0.0.0.0/0` (required for Let's Encrypt HTTP-01 challenges). nginx redirects all HTTP to HTTPS.
 - **Port 443 (HTTPS)** — restrict to your IP if possible. If you need it world-open, `LOCAL_BACKEND_API_KEY` is your primary defense.
 
 ### Install nginx and Certbot
 
 ```bash
-apt-get install -y nginx certbot python3-certbot-nginx
+sudo apt-get install -y nginx certbot python3-certbot-nginx
 ```
 
 ### Configure nginx
 
 Save this at `/etc/nginx/sites-available/canvas.example.com`, replacing the domain: