fix: correct plugin installation command

- Change /install-plugin to /add-marketplace
- Change github:owner/repo format to owner/repo

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: auge2u

README.md

@@ -20,8 +20,8 @@ Both methods configure the same things - choose based on your preference.
 If you have Claude Code, install as a plugin for the full interactive experience:
 
 ```bash
-# Install the plugin
-claude /install-plugin github:auge2u/claude-dev-kit
+# Add the marketplace (run inside Claude Code)
+/add-marketplace auge2u/claude-dev-kit
 ```
 
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