refactor: consolidate plugin.json metadata into marketplace.json

Merge license, homepage, repository, keywords, and author from
plugin.json into marketplace.json and remove the redundant file.
The npx skills installer only reads marketplace.json for skill
discovery — plugin.json contributed no functional value.

Author: bmadcode

.claude-plugin/marketplace.json

@@ -3,12 +3,19 @@
   "owner": {
     "name": "Brian (BMad) Madison"
   },
+  "license": "MIT",
+  "homepage": "https://github.com/bmad-code-org/bmad-module-game-dev-studio",
+  "repository": "https://github.com/bmad-code-org/bmad-module-game-dev-studio",
+  "keywords": ["bmad", "game-dev", "unity", "unreal", "godot", "game-design", "game-architecture"],
   "plugins": [
     {
       "name": "bmad-game-dev-studio",
       "source": "./",
-      "description": "Game development agents and workflows — preproduction, design, architecture, production, and testing for Unity, Unreal, and Godot.",
+      "description": "A comprehensive game development module with agents and workflows for preproduction, design, architecture, production, and testing across Unity, Unreal, and Godot. Part of the BMad Method ecosystem.",
       "version": "0.2.2",
+      "author": {
+        "name": "Brian (BMad) Madison"
+      },
       "skills": [
         "./src/agents/gds-agent-game-architect",
         "./src/agents/gds-agent-game-designer",