refactor(api)!: 平台 id 回退——joox/5sing/bili/apple 恢复全名，目录对齐 bd/mg

- 撤销 3381e9b/1b972ec 中 jx/5s/bl/ap 四个短码，恢复 joox/5sing/bili/apple；
  qian→bd、migu→mg 保留
- 目录与文件对齐保留的新 id：sdk/qian/→sdk/bd/、sdk/migu/→sdk/mg/、
  sdk/apis/qian.ts→bd.ts、migu.ts→mg.ts、src/http/migu-stream.ts→mg-stream.ts
  （规则改为「目录=对外 id」，聚合入口的模块变量同步更名；music.migu.cn 等域名、
  上游 music-lib 对照注释、miguGet 等功能标识符不动）
- 对外 id 全表：kw kg tx wy qs xm me qt lr mg bd joox 5sing bili apple

**破坏性变更**：joox/5sing/bili/apple 四平台的 URL、/sources 返回与
data/auth.json 凭据键恢复全名，已存短码键的登录态需重新登录。

验证：typecheck ✓、pnpm test 112/112 ✓

sdk/mg/lyric.ts

@@ -0,0 +1,42 @@
+// 咪咕歌词 —— resourceinfo.do 取 lrcUrl/lyricUrl 再下载文本
+// 上游对应：music-lib/migu/lyric.go
+import { buildUrl, fetchSongDetail, miguGet } from './util.ts'
+import { httpFetch } from '../common/request.ts'
+
+const LRC_REFERER = 'https://y.migu.cn/'
+const LRC_UA = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36'
+
+/** 从 songmid（contentId|resourceType|formatType）或 extra 取 contentId */
+export const contentIdOf = (songInfo: any): string => {
+  const extra = songInfo?.extra ?? {}
+  if (extra.content_id) return String(extra.content_id)
+  const id = String(songInfo?.songmid ?? songInfo?.id ?? '')
+  return id.split('|')[0] ?? ''
+}
+
+export const getLyric = (songInfo: any) => {
+  const requestObj = { cancelHttp() {}, promise: null as any }
+  const contentID = contentIdOf(songInfo)
+  requestObj.promise = (async() => {
+    if (!contentID) throw new Error('migu 歌曲 id 无效')
+    const body = await miguGet(buildUrl('http://c.musicapp.migu.cn/MIGUM2.0/v1.0/content/resourceinfo.do', {
+      resourceId: contentID,
+      resourceType: '2',
+    }))
+    const resource = body?.resource ?? []
+    if (!resource.length) throw new Error('migu 歌词资源不存在')
+    let lrcUrl = String(resource[0]?.lrcUrl ?? '') || String(resource[0]?.lyricUrl ?? '')
+    if (!lrcUrl) return { lyric: '', tlyric: '' }
+    lrcUrl = lrcUrl.replace(/^http:\/\//, 'https://')
+    const { statusCode, body: lrc } = await httpFetch(lrcUrl, {
+      headers: { 'User-Agent': LRC_UA, Referer: LRC_REFERER },
+      timeout: 20000,
+    }).promise
+    if (statusCode !== 200) throw new Error(`migu 歌词下载失败 ${statusCode}`)
+    return { lyric: typeof lrc === 'string' ? lrc : '', tlyric: '' }
+  })()
+  return requestObj
+}
+
+export { fetchSongDetail }
+export default { getLyric }