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/scripts/build.ts

@@ -0,0 +1,21 @@
+import { mkdir, rm } from 'node:fs/promises'
+
+const ROOT = new URL('../', import.meta.url)
+const DIST = new URL('../dist/', import.meta.url)
+
+await rm(DIST, { recursive: true, force: true })
+await mkdir(DIST, { recursive: true })
+
+// Emit dist/**/*.js + dist/**/*.d.ts (+ maps) via tsc.
+const proc = Bun.spawn(['bunx', 'tsc', '-p', 'tsconfig.build.json'], {
+  cwd: ROOT.pathname,
+  stdout: 'inherit',
+  stderr: 'inherit',
+})
+const exitCode = await proc.exited
+if (exitCode !== 0) {
+  console.error('tsc emit failed')
+  process.exit(exitCode)
+}
+
+console.log('✓ build complete')