feat(showcase): expand feature registry for langgraph-python demo fleet

Adds rows for the demos being built in this branch:

- Split `chat-prebuilt` into `prebuilt-chat`, `prebuilt-sidebar`,
  `prebuilt-popup` (CopilotChat / CopilotSidebar / CopilotPopup).
- Reorder `generative-ui` rows and add: `hitl-in-chat` (In-Chat HITL),
  `gen-ui-interrupt`, `declarative-gen-ui` (Dynamic Schema),
  `a2ui-fixed-schema` (new), `mcp-apps`, `open-gen-ui`, `gen-ui-agent`,
  `tool-rendering`.
- `constraints.yaml`: expand `constrained-explicit` allowlist so the
  langgraph-python manifest validates against the new feature ids.
- Bump expected langgraph-python feature/demo count in
  `generate-registry.test.ts` from 10 -> 22 to match the manifest.

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

Author: ataibarkai

showcase/scripts/__tests__/generate-registry.test.ts

@@ -104,8 +104,8 @@ describe("Registry Generator", () => {
     expect(langgraph.name).toBe("LangGraph (Python)");
     expect(langgraph.category).toBe("popular");
     expect(langgraph.language).toBe("python");
-    expect(langgraph.features.length).toBe(10);
-    expect(langgraph.demos.length).toBe(10);
+    expect(langgraph.features.length).toBe(22);
+    expect(langgraph.demos.length).toBe(22);
   });
 
   it("sorts integrations by sort_order", () => {

showcase/shared/constraints.yaml

@@ -27,12 +27,23 @@ generative_ui:
   constrained-explicit:
     allowed:
       - agentic-chat
+      - agentic-chat-reasoning
+      - prebuilt-chat
+      - prebuilt-sidebar
+      - prebuilt-popup
+      - chat-slots
+      - headless-simple
+      - headless-complete
       - frontend-tools
       - gen-ui-tool-based
       - gen-ui-interrupt
       - gen-ui-agent
       - hitl-in-chat
       - hitl-in-app
+      - declarative-gen-ui
+      - a2ui-fixed-schema
+      - mcp-apps
+      - open-gen-ui
       - tool-rendering
       - useComponent
       - multi-modal

showcase/shared/feature-registry.json

@@ -58,10 +58,22 @@
       "description": "Natural conversation with frontend tool execution"
     },
     {
-      "id": "chat-prebuilt",
-      "name": "Pre-built Chat Components",
+      "id": "prebuilt-chat",
+      "name": "Pre-Built: CopilotChat",
       "category": "chat-ui",
-      "description": "Using CopilotKit's pre-built chat components"
+      "description": "Full-screen/embedded chat via <CopilotChat />"
+    },
+    {
+      "id": "prebuilt-sidebar",
+      "name": "Pre-Built: Sidebar",
+      "category": "chat-ui",
+      "description": "Docked sidebar chat via <CopilotSidebar />"
+    },
+    {
+      "id": "prebuilt-popup",
+      "name": "Pre-Built: Popup",
+      "category": "chat-ui",
+      "description": "Floating popup chat via <CopilotPopup />"
     },
     {
       "id": "chat-slots",
@@ -107,9 +119,15 @@
     },
     {
       "id": "declarative-gen-ui",
-      "name": "Declarative Generative UI (A2UI)",
+      "name": "Declarative Generative UI (A2UI — Dynamic Schema)",
+      "category": "generative-ui",
+      "description": "A2UI rendering where the agent emits schema at runtime"
+    },
+    {
+      "id": "a2ui-fixed-schema",
+      "name": "Declarative Generative UI (A2UI — Fixed Schema)",
       "category": "generative-ui",
-      "description": "Declarative mapping of agent state to rendered components"
+      "description": "A2UI rendering against a known, fixed client-side schema"
     },
     {
       "id": "mcp-apps",