Restructure repo as Claude Code plugin marketplace (#3)

- Move skills/ to plugins/gmx-io/skills/ for plugin format
- Add plugins/gmx-io/.claude-plugin/plugin.json manifest
- Update marketplace.json with correct source field
- Update README with Claude Code install instructions

Author: qwinndev

.claude-plugin/marketplace.json

@@ -7,8 +7,14 @@
   "license": "MIT",
   "plugins": [
     {
-      "name": "gmx-trading",
-      "path": "skills/gmx-trading/SKILL.md"
+      "name": "gmx-io",
+      "source": "./plugins/gmx-io",
+      "description": "Agent skills for trading perpetuals and swapping tokens on GMX V2",
+      "version": "0.1.0",
+      "author": {
+        "name": "gmx-io"
+      },
+      "license": "MIT"
     }
   ]
 }

README.md

@@ -4,6 +4,13 @@ Agent skills for trading on [GMX V2](https://app.gmx.io).
 
 ## Install
 
+**Claude Code (plugin marketplace):**
+```
+/plugin marketplace add gmx-io/gmx-ai
+/plugin install gmx-io@gmx-ai
+```
+
+**Vercel Skills CLI:**
 ```bash
 npx skills add gmx-io/gmx-ai
 ```

plugins/gmx-io/.claude-plugin/plugin.json

@@ -0,0 +1,5 @@
+{
+  "name": "gmx-io",
+  "description": "Agent skills for trading perpetuals and swapping tokens on GMX V2",
+  "version": "0.1.0"
+}