fix: use GitHub source object in marketplace.json

Fixes 'Invalid schema: plugins.0.source: Invalid input' error when
installing via /plugin marketplace add. The source field needs to be
a GitHub source object, not a relative path, when the plugin is at
the repo root.

.claude-plugin/marketplace.json

@@ -11,7 +11,10 @@
   "plugins": [
     {
       "name": "everything-claude-code",
-      "source": ".",
+      "source": {
+        "source": "github",
+        "repo": "affaan-m/everything-claude-code"
+      },
       "description": "Complete collection of agents, skills, hooks, commands, and rules evolved over 10+ months of intensive daily use",
       "version": "1.0.0",
       "author": {