feat(web): redesign install-progress dialog for MCP/skill

The progress dialog showed plugin-only stages (download + dependency install)
for every type. MCP/skill have no such steps, so show a single
"installing → done/failed" row for them (MCP: adding & connecting the server;
skill: installing the package) while keeping the detailed download/deps
stages for plugins.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/i18n/locales/en-US.ts

@@ -1537,6 +1537,11 @@ const enUS = {
     installInfoId: 'ID',
     installInfoVersion: 'Version',
     installSuccess: 'Installed successfully',
+    installStage: {
+      mcpInstalling: 'Adding and connecting the MCP server…',
+      skillInstalling: 'Installing the skill…',
+      installed: 'Done',
+    },
     manualAdd: 'Manual Add',
     uploadExtension: 'Drag & drop or click to upload',
     uploadHint: 'Supports .zip (skills) and .lbpkg (plugins) files',

web/src/i18n/locales/zh-Hans.ts

@@ -1473,6 +1473,11 @@ const zhHans = {
     installInfoId: '标识',
     installInfoVersion: '版本',
     installSuccess: '安装成功',
+    installStage: {
+      mcpInstalling: '正在添加并连接 MCP 服务器…',
+      skillInstalling: '正在安装技能…',
+      installed: '已完成',
+    },
     manualAdd: '手动添加',
     uploadExtension: '拖拽或点击上传扩展包',
     uploadHint: '支持 .zip（技能）和 .lbpkg（插件）文件',