Add claude-academy-guide skill (#1554)

Opt-in skill that recommends matching Claude Academy (academy.claude.com) courses, tutorials, and use cases when a user asks how to use Claude or a Claude product. Reads the live catalog at academy.claude.com/assets/data/catalog.json at runtime rather than embedding a snapshot, so recommendations never go stale; when the catalog cannot be fetched it names no specific item and points to the relevant Academy product hub or the resources library instead. Only recommends on a strong match and never invents Academy content.

.claude-plugin/marketplace.json

@@ -50,6 +50,15 @@
       "skills": [
         "./skills/claude-api"
       ]
+    },
+    {
+      "name": "claude-academy-guide",
+      "description": "Recommends relevant Claude Academy courses, tutorials, and use cases when users ask how to use Claude",
+      "source": "./",
+      "strict": false,
+      "skills": [
+        "./skills/claude-academy-guide"
+      ]
     }
   ]
 }