fix: remove duplicate hooks field from plugin.json

Claude Code automatically loads hooks/hooks.json from the plugin directory.
Explicitly specifying it in plugin.json causes a duplicate hooks error:

  Duplicate hooks file detected: ./hooks/hooks.json resolves to already-loaded
  file .../hooks/hooks.json. The standard hooks/hooks.json is loaded
  automatically, so manifest.hooks should only reference additional hook files.

Fixes #29

.claude-plugin/plugin.json

@@ -24,6 +24,5 @@
     "best-practices"
   ],
   "commands": "./commands",
-  "skills": "./skills",
-  "hooks": "./hooks/hooks.json"
+  "skills": "./skills"
 }