docs: 中性化 README 与代码注释中的第三方客户端引用

- README.md / README_EN.md：桌面 GUI 段落的第三方客户端类比改为中性的「托盘式桌面客户端」，功能说明不变
- cmd/gui 注释、internal/provider 注释：代理示例改为中性的本地 HTTP 代理表述
- internal/lua/plugins/channels.lua、internal/lua/vm.go：注释措辞中性化

仅文案与注释调整，无任何逻辑变更。

cmd/gui/renderer/app.js

@@ -1,5 +1,5 @@
 // ModelRouter Desktop GUI — renderer
-// Clash-Verge-style: the content area is a full-screen iframe loading the
+// Tray-app style: the content area is a full-screen iframe loading the
 // real WebUI 1:1 (status / chat / keys / priority / sources / adapters).
 // The shell only adds the titlebar, settings overlay and tray integration.
 const state = {

cmd/gui/renderer/index.html

@@ -83,7 +83,7 @@
       </div>
     </div>
 
-    <!-- side rail: autostart / silent toggles (Clash-Verge style) -->
+    <!-- side rail: autostart / silent toggles (tray-app style) -->
     <aside class="rail" id="rail">
       <div class="rail-gap"></div>
       <button

cmd/gui/renderer/style.css

@@ -1,5 +1,5 @@
 /* =====================================================================
-   ModelRouter Desktop GUI — Clash-Verge-style shell
+   ModelRouter Desktop GUI — tray-app style shell
    Content area = full-screen iframe embedding the real WebUI 1:1.
    Palette mirrors the WebUI (sakura/frost/glassmorphism).
    ===================================================================== */