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/tsconfig.build.json

@@ -0,0 +1,21 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "noEmit": false,
+    "declaration": true,
+    "declarationMap": false,
+    "sourceMap": false,
+    "outDir": "dist",
+    "rootDir": "src",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "target": "ESNext"
+  },
+  "include": ["src/**/*"],
+  "exclude": [
+    "node_modules",
+    "src/**/__tests__/**",
+    "examples/**",
+    "scripts/**"
+  ]
+}