chore(workflow-engine): 封包发布到 npm

- 移除 private，补全 exports/types/files/publishConfig/license/repository 等
- 添加 LICENSE (MIT) 与 README
- 添加 scripts/build.ts + tsconfig.build.json，用 tsc emit 输出 dist/**/*.js + .d.ts
  （Bun bundle + external zod 会丢失 createWorkflowTool/workflowInputSchema/persistInlineScript 符号，改用 tsc emit）
- 修 src/index.ts 的 WORKFLOW_TOOL_NAME 重复 export；tool/* 的 named re-export 改为 import + 再 export

Co-Authored-By: glm-5.2 <zai-org@claude-code-best.win>

packages/workflow-engine/src/index.ts

@@ -16,10 +16,16 @@ export * from './engine/context.js'
 export * from './engine/hooks.js'
 export * from './engine/runWorkflow.js'
 export * from './progress/events.js'
-export {
+import {
   createWorkflowTool,
   type WorkflowToolDescriptor,
 } from './tool/WorkflowTool.js'
-export { workflowInputSchema, type WorkflowInput } from './tool/schema.js'
-export { persistInlineScript } from './tool/persistInline.js'
-export { WORKFLOW_TOOL_NAME } from './tool/constants.js'
+import { workflowInputSchema, type WorkflowInput } from './tool/schema.js'
+import { persistInlineScript } from './tool/persistInline.js'
+export {
+  createWorkflowTool,
+  type WorkflowToolDescriptor,
+  workflowInputSchema,
+  type WorkflowInput,
+  persistInlineScript,
+}