docs(docs): add strategy, coding, and system design documentation hierarchy

docs/content/02-guides/03-behavioral/meta.ts

@@ -0,0 +1,9 @@
+import { defineMeta } from "blume";
+
+export default defineMeta({
+  title: "Behavioral",
+  order: 3,
+  collapsed: true,
+  icon: "handshake",
+  display: "page",
+});