fix(.claude-plugin): 恢复 marketplace.json source.url 格式

本地 marketplace.json 与 marketplace 仓库用途不同，
恢复 url 格式避免影响用户安装。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: arch-team

.claude-plugin/marketplace.json

@@ -10,8 +10,7 @@
       "description": "Never re-explain your project to Claude again. devpace remembers context across sessions, manages requirement changes, and ensures quality gates — all automatically. Zero setup friction, just /pace-init and start coding.",
       "version": "1.6.3",
       "source": {
-        "source": "github",
-        "repo": "arch-team/devpace",
+        "url": "https://github.com/arch-team/devpace",
         "ref": "v1.6.3"
       },
       "author": {