feat: 视觉能力去 Electron 化，经 HostBridge.screen 注入（迁移阶段1-A9）

- HostBridge 新增可选 screen 服务（listDisplays/primaryDisplay/dipToScreenPoint/
  displayMatching/captureDisplay），vision 3 处、cv-vision 2 处动态 import(electron)
  全部改为 requireScreenService()；未注入时抛稳定的 host_unavailable
- demo 宿主 src/main/index.ts 用 desktopCapturer/screen 实现 screen 服务
- check-deps.mjs 升级：新增动态 import()/require() 扫描（旧正则实测 0 命中的盲区），
  合成用例验证命中，升级后真实源码 0 违规
- 包依赖闭包：补声明 @cantoo/pdf-lib、@napi-rs/canvas、pdfjs-dist
- cv-vision 测试从 vi.mock(electron) 改为宿主桥注入，11/11 通过

src/main/index.ts

@@ -1,4 +1,4 @@
-import { app, BrowserWindow, dialog, ipcMain, screen, shell } from "electron";
+import { app, BrowserWindow, desktopCapturer, dialog, ipcMain, screen, shell } from "electron";
 import path from "node:path";
 import type { AppInfo, AppSettings, FlowDefinition, FlowSaveOptions, FlowSaveResult, FlowSummary, FlowsImportResult } from "../shared/types";
 import {
@@ -24,7 +24,38 @@ import { logMain } from "./logger";
 // 子流程仓库在宿主（flows.ts），包内能力经 host-bridge 取用（阶段 2 正式化 HostBridge）
 setSubflowSource({ listFlows: async () => listFlows(), getFlow: async (id) => getFlow(id) });
 
-// 宿主能力桥（决策点 4 最小面）：人机交互窗口工厂 / DPI 坐标换算 / AI 配置读取
+// 宿主屏幕服务（迁移阶段1-A9）：视觉能力经宿主桥拿 desktopCapturer/screen，Core 零 Electron 依赖
+const hostScreenService = {
+  listDisplays: () =>
+    screen.getAllDisplays().map((display) => ({
+      id: String(display.id),
+      bounds: display.bounds,
+      scaleFactor: display.scaleFactor || 1
+    })),
+  primaryDisplay: () => {
+    const display = screen.getPrimaryDisplay();
+    return { id: String(display.id), bounds: display.bounds, scaleFactor: display.scaleFactor || 1 };
+  },
+  dipToScreenPoint: (point: { x: number; y: number }) => screen.dipToScreenPoint(point),
+  displayMatching: (rect: { x: number; y: number; width: number; height: number }) => {
+    const display = screen.getDisplayMatching(rect);
+    return { id: String(display.id), bounds: display.bounds, scaleFactor: display.scaleFactor || 1 };
+  },
+  captureDisplay: async (displayId: string, wantWidth: number, wantHeight: number): Promise<Uint8Array> => {
+    const sources = await desktopCapturer.getSources({
+      types: ["screen"],
+      thumbnailSize: { width: wantWidth, height: wantHeight }
+    });
+    const source =
+      sources.find((item) => item.display_id === displayId) ||
+      sources.find((item) => item.thumbnail.getSize().width === wantWidth) ||
+      sources[0];
+    if (!source || source.thumbnail.isEmpty()) throw new Error(`无法获取显示器 ${displayId} 的屏幕截图`);
+    return source.thumbnail.toPNG();
+  }
+};
+
+// 宿主能力桥（决策点 4 最小面）：人机交互窗口工厂 / DPI 坐标换算 / AI 配置读取 / 屏幕服务
 setHostBridge({
   createFormWindow: ({ title }) => {
     const win = new BrowserWindow({
@@ -46,7 +77,8 @@ setHostBridge({
   loadAiConfig: () => {
     const ai = loadSettings().aiConfig;
     return { baseUrl: ai.baseUrl ?? "", apiKey: ai.apiKey ?? "", model: ai.model ?? "", visionModel: ai.visionModel ?? "" };
-  }
+  },
+  screen: hostScreenService
 });
 
 let mainWindow: BrowserWindow | null = null;