fix(workspace_files): file list top-align and scrollable (drop filler/height)

wwwroot/api/workspace_files.dspy

@@ -48,7 +48,7 @@ widgets = []
 # 拖拽上传区
 widgets.append({
     "widgettype": "Droppable",
-    "options": {"accepts": ["*"], "padding": "10px", "css": "filler"},
+    "options": {"accepts": ["*"], "padding": "10px"},
     "subwidgets": [
         {"widgettype": "Text", "options": {"text": "📥 拖拽文件到此处上传", "cfontsize": 0.85, "color": "#64748b", "halign": "middle"}}
     ],
@@ -104,6 +104,6 @@ else:
 
 return {
     "widgettype": "VBox",
-    "options": {"css": "filler", "padding": "8px", "gap": "6px", "height": "100%"},
+    "options": {"width": "100%", "padding": "8px", "gap": "6px"},
     "subwidgets": widgets
 }