fix(plugin): remove namespacePolicy from plugin.json to pass schema validation

The plugin.json schema does not allow additionalProperties. Namespace
policy is documented in docs/namespace-policy.md instead.

Author: JeremyDev87

packages/claude-code-plugin/.claude-plugin/plugin.json

@@ -5,11 +5,5 @@
   "author": {
     "name": "JeremyDev87",
     "email": "soundbrokaz@kakao.com"
-  },
-  "namespacePolicy": {
-    "prefix": "codingbuddy",
-    "bareCommandsDeprecated": true,
-    "policyDoc": "docs/namespace-policy.md",
-    "note": "All new commands MUST use the codingbuddy:* namespace. Existing bare commands are migration targets."
   }
 }