Add Multi-CLI Plan feature and corresponding JSON schema

- Introduced a new navigation item for "Multi-CLI Plan" in the dashboard template.
- Created a new JSON schema for "Multi-CLI Discussion Artifact" to facilitate structured discussions and decision-making processes.

ccw/src/templates/dashboard-css/01-base.css

@@ -119,6 +119,14 @@ body {
   color: hsl(var(--orange));
 }
 
+.nav-item[data-lite="multi-cli-plan"].active {
+  background-color: hsl(var(--purple-light, 280 60% 95%));
+}
+
+.nav-item[data-lite="multi-cli-plan"].active .nav-icon {
+  color: hsl(var(--purple, 280 60% 50%));
+}
+
 .sidebar.collapsed .toggle-icon {
   transform: rotate(180deg);
 }