feat: webUI 文本文件编辑/保存 + 相关改动

- FileViewer 新增文本编辑模式（textarea + 保存/取消 + Ctrl+S）
- 后端 /api/files POST 新增 type=write 原子写入
- i18n 补充编辑相关文案（en/zh-CN）
- searxng-search: 加强 web_search 自动搜索条件
- worktree/next.config: 路径比较与 allowedDevOrigins 优化

pi-web/lib/i18n/messages/en.ts

@@ -304,6 +304,16 @@ export const enLocale: LocalePlugin = {
     "i18n.mentionSelectedLines": "Mention selected lines",
     "i18n.disableWrap": "Disable word wrap",
     "i18n.enableWrap": "Enable word wrap",
+    "i18n.editFile": "Edit file",
+    "i18n.stopEditing": "Stop editing",
+    "i18n.saveFile": "Save file",
+    "i18n.saveShortcut": "Save (Ctrl/Cmd+S)",
+    "i18n.discardChanges": "Discard unsaved changes",
+    "i18n.saveError": "Could not save file: {error}",
+    "i18n.closeWithoutSaving": "You have unsaved changes. Discard them and exit editing?",
+    "i18n.editing": "Editing",
+    "i18n.unsaved": "unsaved changes",
+    "i18n.readOnly": "Read-only",
     "i18n.htmlPreview": "HTML preview",
     "i18n.previewFile": "Preview {file}",
     "i18n.invalidMermaid": "Invalid Mermaid diagram",

pi-web/lib/i18n/messages/zh-CN.ts

@@ -304,6 +304,16 @@ export const zhCNLocale: LocalePlugin = {
     "i18n.mentionSelectedLines": "提及所选行",
     "i18n.disableWrap": "禁用自动换行",
     "i18n.enableWrap": "启用自动换行",
+    "i18n.editFile": "编辑文件",
+    "i18n.stopEditing": "停止编辑",
+    "i18n.saveFile": "保存文件",
+    "i18n.saveShortcut": "保存（Ctrl/Cmd+S）",
+    "i18n.discardChanges": "放弃未保存的更改",
+    "i18n.saveError": "无法保存文件：{error}",
+    "i18n.closeWithoutSaving": "您有未保存的更改。放弃并退出编辑？",
+    "i18n.editing": "编辑中",
+    "i18n.unsaved": "未保存的更改",
+    "i18n.readOnly": "只读",
     "i18n.htmlPreview": "HTML 预览",
     "i18n.previewFile": "预览 {file}",
     "i18n.invalidMermaid": "Mermaid 图表无效",

pi-web/lib/worktree.ts

@@ -2,7 +2,7 @@ import { execFile } from "child_process";
 import { existsSync, mkdirSync, realpathSync } from "fs";
 import { basename, dirname, join, resolve } from "path";
 import { promisify } from "util";
-import { allowFileRoot } from "./allowed-roots";
+import { allowFileRoot, normalizeSlashes } from "./allowed-roots";
 
 const execFileAsync = promisify(execFile);
 
@@ -48,6 +48,15 @@ export function invalidateProjectCache(): void {
   globalThis.__piProjectCache?.clear();
 }
 
+/** Path equality that tolerates Windows quirks: git prints forward slashes
+ *  while realpathSync uses backslashes, and drive letters may differ in case. */
+function samePath(a: string, b: string): boolean {
+  if (process.platform === "win32") {
+    return normalizeSlashes(a).toLowerCase() === normalizeSlashes(b).toLowerCase();
+  }
+  return a === b;
+}
+
 async function git(cwd: string, args: string[]): Promise<string> {
   const { stdout } = await execFileAsync("git", ["-C", cwd, ...args], {
     timeout: 10_000,
@@ -99,7 +108,7 @@ export async function resolveProject(cwd: string): Promise<ProjectInfo> {
     // cwd is a subdirectory of a repo keeps its own project identity —
     // grouping subdirs under the repo root would change where new sessions
     // are created for existing users.
-    const isTopLevel = toplevel === realCwd;
+    const isTopLevel = samePath(toplevel, realCwd);
     const isWorktreeTopLevel = gitDir !== commonDir && isTopLevel;
     info = {
       projectRoot: isWorktreeTopLevel ? dirname(commonDir) : cwd,