fix: allow follow-up messages after cancelling remote OpenCode questions

Cancelling a managed SSH prompt while answering a question could leave the conversation bound to its previous operation and reject the next message. Record the Agent cancellation outcome and reconcile and close the desktop binding before the next prompt.

Add two cancellation regressions and document real SSH/Electron question validation across eight theme and viewport combinations. Local queues and remote question routing are already included in 3b560c9.

Validation: prior focused checks passed 275 tests with 5 skipped; typecheck and lint passed. The final full run passed 4087 tests with 66 skipped and one packaging timeout; that packaging file separately passed 22 tests with 1 skipped. Staged diff whitespace check passed.

Release note: After cancelling a pending OpenCode question on a managed SSH task, you can send another message in the same conversation without an operation identity error.

docs/features/remote-host/technical-design.md

@@ -275,6 +275,9 @@ Execute 直接启动已签名 Runtime：
   `127.0.0.1` 的临时 HTTP 入口。该入口使用进程级随机路径，能力 URL 不写入语义记录。
   插件复用 OpenCode 注入客户端的进程内 HTTP 适配器调用 `/question/{id}/reply` 或
   `/reject`；空答案数组表示拒答，非空答案数量须与问题数量一致。问答不经过 ACP 权限审批。
+  用户取消托管 Prompt 时，Agent 同步记录语义终态和操作终态。Desktop 等待取消升级及
+  终态核对后关闭旧 binding、释放会话通道；同一对话的下一条消息使用新 binding，避免
+  将新请求写入仍携带旧 operation ID 的 binding。断线附加原请求的规则保持不变。
 - 语义记录分页另带 Agent 当前 `pendingQuestions`，用于附加同一存活 Prompt 后恢复待答
   问题；历史问答元数据不重新生成表单。原生已回答、拒答、会话空闲、取消、Prompt 终结
   和进程退出清除相应映射，迟到的回答报错。回复失败保留桌面输入供重试，答案不会跨连接