docs: note Lucide source for composer icons

static/ui.js

@@ -1240,6 +1240,8 @@ function getComposerPrimaryAction(){
 }
 
 function _setComposerPrimaryButtonIcon(btn,action){
+  // Queue/interrupt/steer icons are inline Lucide SVGs (ISC):
+  // https://lucide.dev/icons/
   const icons={
     send:'<svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><line x1="12" y1="19" x2="12" y2="5"/><polyline points="5 12 12 5 19 12"/></svg>',
     queue:'<svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M16 5H3"/><path d="M16 12H3"/><path d="M9 19H3"/><path d="m16 16-3 3 3 3"/><path d="M21 5v12a2 2 0 0 1-2 2h-6"/></svg>',