feat: add file edit diff progress view

Capture file edit snapshots through runner tool lifecycle hooks and render unified diffs in the WebUI with folding and truncation controls.

webui/src/i18n/locales/zh-CN/common.json

@@ -141,6 +141,7 @@
       "presetModel": "预设模型",
       "density": "密度",
       "activityMode": "活动详情",
+      "fileEditDisplay": "文件编辑展示",
       "codeWrap": "代码换行",
       "brandLogos": "品牌 Logo",
       "maxResults": "最大结果数",
@@ -187,6 +188,7 @@
       "presetModel": "切回 Default 后可在 WebUI 中编辑模型和提供商。",
       "density": "只保存在此浏览器中。",
       "activityMode": "选择默认显示多少 agent 活动细节。",
+      "fileEditDisplay": "选择文件编辑活动默认显示行数还是差异。",
       "codeWrap": "让长代码行在小屏幕上也易读。",
       "brandLogos": "在设置中显示第三方提供商和 CLI 图标。",
       "maxResults": "每次 web_search 调用返回的结果数。",
@@ -329,6 +331,9 @@
       "compact": "紧凑",
       "auto": "自动",
       "expanded": "展开",
+      "summary": "摘要",
+      "diff": "差异",
+      "collapsedDiff": "折叠差异",
       "on": "开启",
       "off": "关闭",
       "defaultPermission": "默认权限",
@@ -1038,7 +1043,15 @@
     "forkFromHere": "分叉",
     "copyReply": "复制",
     "copiedReply": "已复制",
-    "turnLatencyTitle": "本轮耗时（端到端）"
+    "turnLatencyTitle": "本轮耗时（端到端）",
+    "fileEditViewDiff": "查看差异",
+    "fileEditViewLargeDiff": "查看大型差异",
+    "fileEditDiffLineCount": "{{count}} 行",
+    "fileEditUnchangedLinesHidden": "已隐藏 {{count}} 行未修改内容",
+    "fileEditShowMoreLines": "显示剩余 {{count}} 行",
+    "fileEditShowFewerLines": "收起部分行",
+    "fileEditOpenFile": "打开文件",
+    "fileEditDiffTruncated": "差异内容已截断。打开文件可查看完整更改。"
   },
   "lightbox": {
     "title": "图片预览",