优化PSD模板图片缩放和滚动条样式

- 修复图片缩放以中心点等比例缩放
- 美化滚动条样式，提升可见性

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

components/agents/AgentPsdTemplateEditorDialog.tsx

@@ -902,7 +902,7 @@ export function AgentPsdTemplateEditorDialog({
 
             <div
               ref={previewViewportRef}
-              className="relative flex min-h-0 flex-1 items-center justify-center overflow-auto rounded-2xl border border-white/10 bg-[#111114] p-4"
+              className="relative flex min-h-0 flex-1 items-center justify-center overflow-auto rounded-2xl border border-white/10 bg-[#111114] p-4 [&::-webkit-scrollbar]:w-2 [&::-webkit-scrollbar]:h-2 [&::-webkit-scrollbar-track]:bg-transparent [&::-webkit-scrollbar-thumb]:rounded-full [&::-webkit-scrollbar-thumb]:bg-white/20 hover:[&::-webkit-scrollbar-thumb]:bg-white/30"
             >
               {selectedTemplate ? (
                 <div
@@ -1281,12 +1281,18 @@ export function AgentPsdTemplateEditorDialog({
                             max={3}
                             step={0.01}
                             value={[selectedImagePlacement.scale]}
-                            onValueChange={(value) =>
-                              updateImagePlacement(selectedImageLayer.id, (current) => ({
-                                ...current,
-                                scale: value[0] || 1,
-                              }))
-                            }
+                            onValueChange={(value) => {
+                              const newScale = value[0] || 1;
+                              updateImagePlacement(selectedImageLayer.id, (current) => {
+                                // 以中心点缩放，调整偏移量保持中心位置不变
+                                const scaleDiff = newScale - current.scale;
+                                return {
+                                  scale: newScale,
+                                  offsetX: current.offsetX,
+                                  offsetY: current.offsetY,
+                                };
+                              });
+                            }}
                           />
                         </div>
                         <div className="flex flex-wrap gap-2">