feat: harden workspace file APIs

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/api/file_handler.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"net/http"
+	"time"
 
 	"codespace/internal/model"
 	"codespace/internal/service"
@@ -112,3 +113,24 @@ func (h *fileHandler) rename(c *gin.Context) {
 	}
 	c.Status(http.StatusNoContent)
 }
+
+func (h *fileHandler) stat(c *gin.Context) {
+	id := c.Param("id")
+	path := c.Query("path")
+	if path == "" {
+		writeBadRequest(c, "path is required")
+		return
+	}
+	info, err := h.svc.Stat(id, path)
+	if err != nil {
+		writeError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, model.FileInfoResponse{
+		Name:    info.Name,
+		Path:    info.Path,
+		IsDir:   info.IsDir,
+		Size:    info.Size,
+		ModTime: info.ModTime.Format(time.RFC3339Nano),
+	})
+}