docs: add Linux npm permissions guidance and prerequisites section

README.md

@@ -48,6 +48,20 @@ Think of it as a senior developer pair-programming with you, but it never sleeps
 
 ## Quick Start
 
+### Prerequisites
+
+- **Node.js v18+** (includes npm) — [nodejs.org](https://nodejs.org/)
+- An API key from a supported provider (Venice AI, OpenAI, Anthropic, etc.)
+
+> **Linux users:** Before installing, fix npm global permissions to avoid `EACCES` errors:
+> ```bash
+> mkdir ~/.npm-global
+> npm config set prefix '~/.npm-global'
+> echo 'export PATH=~/.npm-global/bin:$PATH' >> ~/.bashrc
+> source ~/.bashrc
+> ```
+> This only needs to be done once. Alternatively you can use `sudo npm install -g ...` but the prefix fix is cleaner.
+
 ### Install
 
 ```bash