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。

internal/lua/vm.go

@@ -41,7 +41,7 @@ import (
 var bundledAdapters embed.FS
 
 // adapterGlobal is the reserved global holding the adapter table after the
-// worker boots the script. A reserved name avoids clashing with user code.
+// worker boots the script. A reserved name avoids conflicting with user code.
 const adapterGlobal = "__llmsproxy_adapter"
 
 type APIAdapter struct {