阶段1-rpa-core建包: engine+31个纯Node能力迁入packages/rpa-core, 领域类型单一源化, createEngine工厂收拢模块级状态

- engine/(registry/types/runtime/expression)物理迁入包, 解耦shared/types(域类型归包, 宿主type-only re-export)
- 31个纯Node能力+27个测试迁入包; 宿主留守Electron/浏览器/AI依赖能力, index.ts经@rpa/core/capabilities拉起
- 新增createEngine()/defaultEngine: excel缓存/Excel句柄/db连接/FTP客户端/OCR实例/拟真设置挂引擎实例
- remaining-core子流程依赖改为host-bridge注入, 包内不再import宿主flows
- 宿主main/index.ts启动时注入子流程源; electron-vite/vitest/tsconfig配@rpa/core源码别名
- 验证: typecheck绿, 快照909个id diff为零, 332测试过(2个桌面冒烟因会话无交互SetForegroundWindow被拒, 环境阻塞)

packages/rpa-core/src/index.ts

@@ -0,0 +1,43 @@
+/**
+ * @rpa/core 包入口。
+ *
+ * 只导出引擎 API 与类型，不做能力注册副作用；
+ * 纯 Node 能力通过 `@rpa/core/capabilities` 子路径按需拉起（保持与 demo 宿主
+ * src/main/capabilities/index.ts 相同的副作用注册模型，见任务 4.2 再显式化）。
+ */
+export { createEngine, defaultEngine, RpaEngine, type ManualOperationSettings } from "./engine/engine";
+export { register, getHandler, hasCapability, capabilityIds, capabilityCount } from "./engine/registry";
+export { runFlow } from "./engine/runtime";
+export { RuntimeError, BreakSignal, ContinueSignal, StopSignal, asRuntimeError } from "./engine/types";
+export { setSubflowSource, getSubflowSource, type SubflowSource } from "./engine/host-bridge";
+// PowerShell 助手（阶段 3 将移入 driver/windows/）：宿主留守能力（window-extended 等）经此引用
+export { powershell, psString } from "./capabilities/desktop";
+export type {
+  BrowserLike,
+  BrowserTabInfo,
+  BrowserElementReference,
+  BrowserElementInfo,
+  BrowserSelectOption,
+  BrowserSelectState,
+  BrowserSimilarElementOptions,
+  BrowserElementRegion,
+  RunContext,
+  CapabilityHandler,
+  NodeState,
+  RunResult
+} from "./engine/types";
+export type {
+  CatalogWidget,
+  CatalogField,
+  CatalogOutput,
+  CatalogComponent,
+  CatalogGroup,
+  Catalog,
+  FlowVariable,
+  FlowNodeOptions,
+  FlowNode,
+  FlowEdge,
+  FlowDefinition,
+  RunError,
+  RunEvent
+} from "./types";