feat: add comprehensive testing documentation page with metrics and pipeline details

Author: mikerb95

src/components/DocsNav.astro

@@ -11,6 +11,7 @@ const tabs = [
   { href: '/docs/diagrama-clases', label: 'Clases' },
   { href: '/docs/diagrama-objetos', label: 'Objetos' },
   { href: '/docs/kanban', label: 'Kanban' },
+  { href: '/docs/testing', label: 'Testing' },
   { href: '/docs/usability-testing', label: 'Usability testing' },
 ]