feat(docs): add NavGrid/NavCard components and restructure stage pages

- Add NavGrid.vue and NavCard.vue components for better navigation layout
- Restructure stage-0 index pages across languages into intro.md with new navigation components
- Remove old stage-0 index.md files and update stage-3 pages similarly
- Add new dependencies 'claude' and 'codex' to package.json
- Improve code formatting in multiple Vue components for better readability
- Update documentation content and structure for better user experience

docs/.vitepress/theme/style.css

@@ -270,7 +270,10 @@
 
 /* System Font Stack */
 :root {
-  --vp-font-family-base: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
+  --vp-font-family-base:
+    -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Segoe UI', Roboto,
+    Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji',
+    'Segoe UI Symbol';
 }
 
 /* Glassmorphism Utilities */
@@ -304,7 +307,9 @@
   border-radius: 20px;
   background-image: linear-gradient(to right, #42d392, #647eff);
   border: none;
-  transition: transform 0.2s, opacity 0.2s;
+  transition:
+    transform 0.2s,
+    opacity 0.2s;
 }
 
 .VPHomeHero .action .VPButton.brand:hover {