fix(shell-docs): unpromote interrupt-based — it's LangGraph-specific, not framework-agnostic

The earlier `unselected/` cleanup pass categorized
`unselected/generative-ui/your-components/interrupt-based.mdx` as
D-promote (unique content, needs new home at root). On closer
inspection the file is byte-identical to
`integrations/langgraph/human-in-the-loop/interrupt-flow.mdx` (modulo
title), and references LangGraph's `interrupt()` API + LangChain
interrupt docs throughout — it's LangGraph-specific, not a
framework-agnostic generative-UI feature.

Mastra has its own different interrupt-flow.mdx (264L vs 403L). Other
frameworks (ag2, agno, adk, llamaindex, etc.) don't have an interrupt
flow at all because their agent runtimes don't expose the concept.
Putting it at root would mislead users on other frameworks into
expecting an API that doesn't exist for them.

Reversing the promotion:

- Delete `generative-ui/your-components/interrupt-based.mdx` from the
  root tree
- Drop `interrupt-based` from `generative-ui/your-components/meta.json`
- Repoint the `/unselected/.../interrupt-based` redirect to
  `/human-in-the-loop` (the framework-agnostic HITL page) instead of
  the now-deleted root location

LangGraph's interrupt page stays reachable at
`/langgraph-python/human-in-the-loop/interrupt-flow` (sidebar entry
"Interrupts" under the LangGraph framework block). Mastra's stays at
`/mastra/human-in-the-loop/interrupt-flow`. The `unselected/` copy was
just a redundant fork that was never visible in nav anyway.

Updates the verified-audit framing recorded in PDX-49 — the "13
unique promotions" count drops to 12 (the tutorials), and a new
D-delete entry replaces the interrupt-based promotion.

Author: samjulien

showcase/shell-docs/next.config.ts

@@ -154,11 +154,17 @@ const nextConfig: NextConfig = {
         destination: "/tutorials/:path*",
         permanent: true,
       },
+      // Interrupt-based was a LangGraph-specific page parked in
+      // unselected/. Real homes are
+      // `/<langgraph-slug>/human-in-the-loop/interrupt-flow` (and the
+      // Mastra equivalent). Send anyone landing on the legacy URL to
+      // the framework-agnostic HITL page; soft-default routes them
+      // through to the right framework's interrupt flow if they're
+      // stored as LangGraph or Mastra.
       {
         source:
           "/unselected/generative-ui/your-components/interrupt-based",
-        destination:
-          "/generative-ui/your-components/interrupt-based",
+        destination: "/human-in-the-loop",
         permanent: true,
       },
       // agent-app-context was concept-per-framework only; no canonical