优化：工具栏高度对齐+面板统一+远程连接架构+自动恢复预览

- 工具栏：面包屑与右侧组件像素级等高(:deep 34px)、合并重复search handler、统一分隔符样式、删除死代码
- 面板对齐：三面板header统一padding/font-size、文件列表分页固定底部(自定义紧凑)、表头默认隐藏、滚动条统一样式
- 预览区：始终显示空白预览面板、重启自动恢复上次打开文件
- 收藏夹：简化计数显示(共N项)
- 远程连接：ConnectionIndicator自适应UI(无远程显示mini云图标)、ConnectionDialog支持编辑配置、transport抽象层(本地Wails/远程HTTP双模式)、agent后端模块

internal/agent/handler/server_handler.go

@@ -0,0 +1,64 @@
+package handler
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"path/filepath"
+	"strings"
+
+	"github.com/labstack/echo/v4"
+)
+
+// FileServerProxy 反向代理到内置文件服务器（用于媒体预览）
+func (h *Handler) FileServerProxy(c echo.Context) error {
+	rawPath := c.Param("*")
+	if rawPath == "" {
+		return c.String(http.StatusBadRequest, "缺少文件路径")
+	}
+
+	clean := filepath.Clean(rawPath)
+	if strings.Contains(clean, "..") {
+		return c.String(http.StatusForbidden, "路径不允许包含 ..")
+	}
+
+	// 防止多重 /localfs/ 前缀（循环去除所有）
+	targetPath := filepath.ToSlash(clean)
+	for strings.HasPrefix(targetPath, "localfs/") || strings.HasPrefix(targetPath, "localfs\\") {
+		targetPath = strings.TrimPrefix(targetPath, "localfs/")
+		targetPath = strings.TrimPrefix(targetPath, "localfs\\")
+	}
+	c.Request().URL.Path = "/localfs/" + targetPath
+	h.fileProxy.ServeHTTP(c.Response(), c.Request())
+	return nil
+}
+
+// HTMLPreviewProxy 代理 HTML 预览请求（直连内部服务器，避免 ReverseProxy 路径拼接问题）
+func (h *Handler) HTMLPreviewProxy(c echo.Context) error {
+	rawPath := c.QueryParam("path")
+	if rawPath == "" {
+		return c.String(http.StatusBadRequest, "缺少 path 参数")
+	}
+	clean := filepath.Clean(rawPath)
+	if strings.Contains(clean, "..") {
+		return c.String(http.StatusForbidden, "路径不允许包含 ..")
+	}
+	theme := c.QueryParam("theme")
+
+	targetURL := fmt.Sprintf("http://localhost:8073/localfs/html-preview?path=%s&theme=%s",
+		url.QueryEscape(clean), url.QueryEscape(theme))
+
+	resp, err := http.Get(targetURL)
+	if err != nil {
+		return c.String(http.StatusBadGateway, "内部服务器不可用")
+	}
+	defer resp.Body.Close()
+
+	for k, v := range resp.Header {
+		c.Response().Header()[k] = v
+	}
+	c.Response().WriteHeader(resp.StatusCode)
+	io.Copy(c.Response(), resp.Body)
+	return nil
+}