Implement M1.5 visual design foundation: tokens, IBM Plex, theme toggle, chart themes

src/app/components/SpecEditor.tsx

@@ -42,6 +42,9 @@ export function SpecEditor() {
       language: 'json',
       automaticLayout: true,
       minimap: { enabled: false },
+      // The editor is a Plex Mono surface per the design language (doc §3.1).
+      // Monaco needs an explicit family string — it can't read the CSS token.
+      fontFamily: "'IBM Plex Mono', ui-monospace, 'SF Mono', Menlo, monospace",
       fontSize: 13,
       tabSize: 2,
       wordWrap: 'on',
@@ -78,7 +81,7 @@ export function SpecEditor() {
 
   // Editor theme follows the UI theme (M1: light/dark stock themes).
   useEffect(() => {
-    monaco.editor.setTheme(uiTheme === 'experimental' ? 'vs-dark' : 'vs');
+    monaco.editor.setTheme(uiTheme === 'dark' ? 'vs-dark' : 'vs');
   }, [uiTheme]);
 
   return (