chore(shell-docs): hide and clean up stale pages

Drop orphaned/broken/AI-slop pages from nav, add 302 redirects, and
delete dead per-framework override stragglers. Items addressed:

- 1.1: Tutorials section hidden (broken end-to-end; rewrite post-launch)
- 6.1: coding-agent-setup.mdx (rename straggler -> /coding-agents)
- 10.1: copilot-suggestions.mdx (orphaned broken stub)
- 11.1: generative-ui/open-json-ui.mdx (AI-slop placeholder)
- 21.1: migrate/1.10.X.mdx (~1yr-old migration target)
- 16.1: 3 orphan shared-state files in adk/langgraph/llamaindex
  (each meta.json wires only one of state-inputs-outputs vs
  workflow-execution; the other was a dead duplicate)

All redirects use permanent: false (302) so URLs can be restored at
the same paths once the affected pages are properly authored.

Author: samjulien

showcase/shell-docs/next.config.ts

@@ -316,6 +316,44 @@ const nextConfig: NextConfig = {
         destination: "/concepts/generative-ui-overview",
         permanent: true,
       },
+
+      // Stale pages hidden pre-launch. 302 (not permanent) — these
+      // URLs may be restored once the underlying content is rewritten.
+      // Tutorials are broken end-to-end and pulled from nav; files
+      // remain on disk under content/docs/tutorials/ for post-launch
+      // rewrite.
+      {
+        source: "/tutorials/:path*",
+        destination: "/",
+        permanent: false,
+      },
+      // Old-name straggler from the coding-agents rename; the page
+      // moved to /coding-agents.
+      {
+        source: "/coding-agent-setup",
+        destination: "/coding-agents",
+        permanent: false,
+      },
+      // Orphaned broken stub.
+      {
+        source: "/copilot-suggestions",
+        destination: "/",
+        permanent: false,
+      },
+      // AI-slop placeholder pulled from nav until properly authored;
+      // file stays on disk for rewrite.
+      {
+        source: "/generative-ui/open-json-ui",
+        destination: "/generative-ui",
+        permanent: false,
+      },
+      // ~1-year-old migration target, no longer a meaningful jump-off
+      // point.
+      {
+        source: "/migrate/1.10.X",
+        destination: "/migrate",
+        permanent: false,
+      },
     ];
   },
 };

showcase/shell-docs/src/content/docs/coding-agent-setup.mdx

@@ -12,7 +12,6 @@
     "a2ui",
     "a2ui/dynamic-schema",
     "a2ui/fixed-schema",
-    "open-json-ui",
     "---Open-Ended---",
     "mcp-apps"
   ]