feat: 拦截聊天区文件打开 — 聊天里的文件点击默认开进侧边栏编辑器

包装 ctx.workspaces.openPath（聊天区文件打开的唯一漏斗），接管时
经 openSidebarFile 开进 sidebar 编辑器而非系统默认应用；由
interceptOpenPath pref（默认开）与 editor tab 启用态双重门控，
拒接时原样放行，dispose 还原原始方法引用（HMR 安全）。

- prefs-shared/config/prefs: 新增 interceptOpenPath 字段（默认 true）
- openpath-intercept.ts: 零依赖包装器，纯插件层面实现，不改 DSH
- intercept.tsx: registerOpenPathInterception 接线（当前会话 scope）
- SideCardSection: 常规区新增开关卡片（zh/en 文案）
- 测试: 包装器单测 6 个 + 接线集成测试 + pref 解析/设置页断言更新

src/prefs-shared.ts

@@ -27,6 +27,14 @@ export interface SidebarPrefs {
    * user explicitly enables it in the side card settings.
    */
   agentTerminalTools: boolean
+  /**
+   * Whether chat-side file opens (tool-row path links, the produced-files
+   * row, prose file mentions — every path that funnels through the client
+   * runtime's `ctx.workspaces.openPath`) open in the sidebar editor instead
+   * of the Host OS's default application. On by default; the editor tab's
+   * own enable switch gates it too (both must be on for the takeover).
+   */
+  interceptOpenPath: boolean
   /**
    * Per-tab enable switches, keyed by tab descriptor id (`'explorer'`,
    * `'my-plugin:db'`). An ABSENT key means enabled — only an explicit
@@ -57,6 +65,7 @@ export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   defaultWidthPercent: WIDTH_PERCENT_DEFAULT,
   autoOpenSubagent: true,
   agentTerminalTools: false,
+  interceptOpenPath: true,
   tabsEnabled: {},
   viewersEnabled: {},
 }