docs: simplify opencode readme instructions to match codex style

README.md

@@ -65,7 +65,7 @@ Fetch and follow instructions from https://raw.githubusercontent.com/obra/superp
 Tell OpenCode:
 
 ```
-Clone https://github.com/obra/superpowers to ~/.config/opencode/superpowers, then create directory ~/.config/opencode/plugin, then symlink ~/.config/opencode/superpowers/.opencode/plugin/superpowers.js to ~/.config/opencode/plugin/superpowers.js, then restart opencode.
+Fetch and follow instructions from https://raw.githubusercontent.com/obra/superpowers/refs/heads/main/.opencode/INSTALL.md
 ```
 
 **Detailed docs:** [docs/README.opencode.md](docs/README.opencode.md)