refactor: 解耦 MachineIdTool 插件

- 移除 release workflow 中的插件打包步骤
- 更新插件下载 URL 指向 MachineIdTool 仓库
- 删除本地 plugins/machine-id-tool 目录
- 插件包现由 MachineIdTool 仓库独立管理

plugins/machine-id-tool/config.json

@@ -1,4 +0,0 @@
-{
-  "enabled": true,
-  "settings": {}
-}

plugins/machine-id-tool/plugin.json

@@ -1,32 +0,0 @@
-{
-  "name": "machine-id-tool",
-  "version": "0.2.0",
-  "description": "Machine ID 管理工具 - 查看、修改和管理系统机器码，支持跨平台操作",
-  "author": "ProxyCast Team",
-  "homepage": "https://github.com/aiclientproxy/MachineIdTool",
-  "license": "MIT",
-  "plugin_type": "binary",
-  "entry": "machine-id-tool-cli",
-  "hooks": [],
-  "min_proxycast_version": "1.0.0",
-  "binary": {
-    "binary_name": "machine-id-tool-cli",
-    "github_owner": "aiclientproxy",
-    "github_repo": "MachineIdTool",
-    "platform_binaries": {
-      "macos-arm64": "machine-id-tool-aarch64-apple-darwin",
-      "macos-x64": "machine-id-tool-x86_64-apple-darwin",
-      "linux-x64": "machine-id-tool-x86_64-unknown-linux-gnu",
-      "linux-arm64": "machine-id-tool-aarch64-unknown-linux-gnu",
-      "windows-x64": "machine-id-tool-x86_64-pc-windows-msvc.exe"
-    },
-    "checksum_file": "checksums.txt"
-  },
-  "ui": {
-    "surfaces": ["tools"],
-    "icon": "Cpu",
-    "title": "机器码管理工具",
-    "default_width": 800,
-    "default_height": 600
-  }
-}