Update build instructions: just 'mk' from root

README.md

@@ -23,21 +23,22 @@ git submodule update --init --recursive
 
 ## Building
 
-Each submodule is a standalone project:
+Build everything from the monorepo root:
 
 ```bash
-# Core library
-cd core && mk
-
-# Terminal UI
-cd ../tui && mk
-
-# 9p filesystem server
-cd ../9p && mk
-
-# Emacs Lisp (load ollie.el in Emacs)
+mk
 ```
 
+Or build specific components:
+
+```bash
+mk core    # Build core library
+mk tui     # Build terminal UI
+mk 9p      # Build 9p filesystem server
+```
+
+For Emacs Lisp, load `el/ollie.el` in Emacs.
+
 ## Development
 
 Update all submodules to latest: