refactor: 架构整固——分层单向化、全量 TypeScript、直接运行

- 移除 bd/mg 两平台及磁盘残留产物；清理 api-test 死脚本、musicSdk/message+options 死模块、infSign vendor
- musicSdk/ 改名 sdk/；src/common、src/auth、src/apis 整体移入 sdk/，依赖方向定为 src → sdk 严格单向
- src/ 手写 JS 全量转 .ts，删除 JS 类型垫片 modules.d.ts；源码 import 统一 .ts 后缀
- Node 原生类型剥离直接运行 .ts（engines >=22.18），取消 tsc 发射产物，tsc 仅类型检查（pnpm typecheck）
- 删除 kwdes 备用实现与 src/index.ts 转发垫片；测试移至 test/smoke-test.ts
- common/request.ts 补显式导出类型；修复 set-cookie 单值形态、ApiError 类字段等隐患

验证：tsc 零错误，smoke-test 41/41

sdk/utils.ts

@@ -0,0 +1,60 @@
+import crypto from 'crypto'
+import dns from 'dns'
+import { decodeName } from './common/utils.ts'
+
+export const toMD5 = (str: string): string => crypto.createHash('md5').update(str).digest('hex')
+
+interface CachedIp {
+  address: string
+  family: number
+}
+
+const ipMap = new Map<string, CachedIp | true>()
+
+export const getHostIp = (hostname: string): CachedIp | undefined => {
+  const result = ipMap.get(hostname)
+  if (typeof result === 'object') return result
+  if (result === true) return
+  ipMap.set(hostname, true)
+  dns.lookup(hostname, {
+    // family: 4,
+    all: false,
+  }, (err, address, family) => {
+    if (err) return console.log(err)
+    ipMap.set(hostname, { address, family })
+  })
+}
+
+export const dnsLookup = (
+  hostname: string,
+  options: dns.LookupOptions,
+  callback: (err: NodeJS.ErrnoException | null, address: string, family: number) => void,
+): void => {
+  const result = getHostIp(hostname)
+  if (result) return callback(null, result.address, result.family)
+
+  dns.lookup(hostname, options, callback as any)
+}
+
+/**
+ * 格式化歌手
+ * @param singers 歌手数组或字符串
+ * @param nameKey 歌手名键值
+ * @param join 歌手分割字符
+ */
+export const formatSingerName = (
+  singers: Array<Record<string, unknown>> | string | null | undefined,
+  nameKey = 'name',
+  join = '、',
+): string => {
+  if (Array.isArray(singers)) {
+    const singer: string[] = []
+    singers.forEach(item => {
+      const name = item[nameKey]
+      if (!name) return
+      singer.push(String(name))
+    })
+    return decodeName(singer.join(join))
+  }
+  return decodeName(String(singers ?? ''))
+}