Put 2 child limit dashboard as a research tile in the app

changelog_entry.yaml

@@ -1,5 +1,4 @@
 - bump: minor
   changes:
     added:
-      - UK two-child limit policy comparison app as a featured tile
-      - Slug validation test to prevent conflicts between app slugs and post filenames
+      - UK two-child limit policy comparison dashboard as a featured tile on UK homepage

src/posts/posts.json

@@ -1,4 +1,15 @@
 [
+  {
+    "_comment": "This post uses external_url to link to an interactive app instead of a markdown article. The filename is 'dummy' because no markdown file exists - it redirects directly to the app.",
+    "title": "Two-child limit calculator",
+    "description": "Explore policy reforms to the two-child benefit limit and their impacts on households, government spending, and child poverty.",
+    "date": "2025-10-28",
+    "tags": ["uk", "featured", "policy", "interactives"],
+    "filename": "uk-two-child-limit-comparison-dummy.md",
+    "external_url": "/uk/two-child-limit-comparison",
+    "image": "young-child-exemption-two-child-limit.jpg",
+    "authors": ["vahid-ahmadi"]
+  },
   {
     "title": "Marginal tax rates in California's proposed billionaire tax",
     "description": "The 5% tax creates marginal tax rates between 50% and 60% on wealth between $1 billion and $1.1 billion.",