fix: switch Hugo to CSS class-based syntax highlighting

Set noClasses=false so Hugo outputs Chroma CSS classes instead of
inline styles. 10-chroma.css now drives all syntax colors using
ASW's --syntax-* tokens. Fixed remaining primitive leaks
(--violet-4, --orange-3 → --syntax-keyword, --syntax-variable).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

site/hugo.toml

@@ -30,7 +30,7 @@ title = 'ASW — Agentic Semantic Web'
   ordered    = false
 
 [markup.highlight]
-  noClasses   = true
+  noClasses   = false
   codeFences  = true
   guessSyntax = true