fix(showcase/shell): redirect /<framework>/unselected/<path> → /<framework>/<path>

A framework-scoped URL asserting "unselected" in its path is
incoherent — you can't be both on langgraph-python AND in the
no-framework state. Collapse the redundant segment: if the framework
catch-all receives a slug that starts with unselected/, permanent-
redirect to the same path without that prefix (the framework-scoped
version serves the same content, just with Snippets resolved against
the selected framework's cells).

/docs/unselected/<path> remains a valid framework-agnostic URL.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ataibarkai

showcase/shell/src/app/[framework]/[[...slug]]/page.tsx

@@ -16,7 +16,7 @@
 // none of which are framework slugs, so there are no collisions.
 
 import React from "react";
-import { notFound } from "next/navigation";
+import { notFound, redirect } from "next/navigation";
 import Link from "next/link";
 import { DocsPageView } from "@/components/docs-page-view";
 import { SidebarFrameworkSelector } from "@/components/sidebar-framework-selector";
@@ -73,6 +73,15 @@ export default async function FrameworkScopedDocsPage({
     return <FrameworkLandingPage framework={framework} />;
   }
 
+  // `/<framework>/unselected/<path>` is incoherent — a framework IS
+  // selected, so the URL should never assert the "unselected" state
+  // alongside. Collapse to the framework-scoped path (which serves the
+  // same underlying content, just with Snippets resolved against the
+  // selected framework's cells).
+  if (slugPath.startsWith("unselected/")) {
+    redirect(`/${framework}/${slugPath.slice("unselected/".length)}`);
+  }
+
   // When the page doesn't exist at all, 404.
   const doc = loadDoc(slugPath);
   if (!doc) notFound();