✨ feat(vscode): 工单移交的会话包改走阿里云 OSS、换 xz 压缩，两边进度一步步显示

- 会话包传到 OSS 的 spx-handoff/<owner>/<repo>/issue-<N>-<时间>.tar.xz，上传时对象设成私有；不再挂 Gitea 工单附件
- 新命令「配置移交存储」：endpoint、bucket 存扩展设置，AccessKey 存密钥存储；没配时移交 / 接管直接提示，什么都不改
- 共享 state 字段 handoffAttachmentId 改名 handoffBundleKey（含 spx CLI 与 schema）
- 打包换成 xz 1 级（tar -cJf），去掉 100MB 上限检查和先试压一遍的重复压缩
- 发送方提示打包 / 上传了多少 MB；接管方同一条提示依次显示下载、解包、建 worktree、装会话，完成前不消失
- 会话交接（单会话）仍走 Gitea 附件，Gitea 附件白名单没有 .xz，单独保留 gzip 打包

vscode/webview-ui/src/lib/messages.ts

@@ -93,7 +93,7 @@ export type ExtensionToWebview
     | { type: 'issues/loaded' }
     | { type: 'issues/update', issues: Issue[], scope: 'mine' | 'all', globalAutoReview: boolean, youtrackConfigured: boolean, me?: string, avatars?: Record<string, string> }
     | { type: 'issues/error', message: string }
-    | { type: 'issue/patch', issueNumber: number, patch: { autoReview?: boolean, reviewPassed?: boolean, specFile?: string, planFile?: string, prototypeFile?: string, prDiffFile?: string | null, sessionId?: string | null, implementSessionId?: string | null, reviewSessionId?: string | null, missingSessionIds?: string[], testSessionId?: string | null, prototypeSessionId?: string | null, pr?: string | null, implementStatus?: 'running' | 'done' | 'failed' | null, column?: IssueColumn, worktreePath?: string | null, prMerged?: boolean, prMergedAt?: string | null, branch?: string | null, color?: string, worktreeExists?: boolean, brainstormTabOpen?: boolean, implementTabOpen?: boolean, reviewTabOpen?: boolean, testTabOpen?: boolean, prototypeTabOpen?: boolean, profilePath?: string | null, brainstormProfilePath?: string | null, testProfilePath?: string | null, prototypeProfilePath?: string | null, assignees?: string[], handoffAttachmentId?: string | null, handoffFrom?: string | null, handoffRequestFrom?: string | null, handoffRequestError?: string | null } }
+    | { type: 'issue/patch', issueNumber: number, patch: { autoReview?: boolean, reviewPassed?: boolean, specFile?: string, planFile?: string, prototypeFile?: string, prDiffFile?: string | null, sessionId?: string | null, implementSessionId?: string | null, reviewSessionId?: string | null, missingSessionIds?: string[], testSessionId?: string | null, prototypeSessionId?: string | null, pr?: string | null, implementStatus?: 'running' | 'done' | 'failed' | null, column?: IssueColumn, worktreePath?: string | null, prMerged?: boolean, prMergedAt?: string | null, branch?: string | null, color?: string, worktreeExists?: boolean, brainstormTabOpen?: boolean, implementTabOpen?: boolean, reviewTabOpen?: boolean, testTabOpen?: boolean, prototypeTabOpen?: boolean, profilePath?: string | null, brainstormProfilePath?: string | null, testProfilePath?: string | null, prototypeProfilePath?: string | null, assignees?: string[], handoffBundleKey?: string | null, handoffFrom?: string | null, handoffRequestFrom?: string | null, handoffRequestError?: string | null } }
     /** 某个会话 id 的开 tab 请求已处理完（开成、复用或被拒都算），webview 据此停掉行内 spinner。 */
     | { type: 'session/tab-settled', sessionId: string }
     | { type: 'issue/pr-diff-summary-done', issueNumber: number }