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- 新增 `DirectTurnFailureKind`,成为 `DirectTurnFailure.kind` 的唯一取值表:`timeout / model-failed / transport-failed / request-rejected / environment-not-ready / turn-interrupted / host-dropped`(补齐原先两份注释都漏掉的 `turn-interrupted`) - `DirectModelCallKind::wire_kind` 与 `DirectTurnError::wire_kind` 改成返回该枚举,`DirectTurnFailure::new` / `DirectTurnTerminal::host_dropped` 同步改签名;线上取值仍是原来的 kebab-case 字符串 - 补 `failure_kind_wire_values_are_stable` 用例:7 个变体的序列化 / 反序列化取值逐条钉住,改名即改协议会先在这里失败 - 前端生成绑定重新导出:`chat/generated/DirectTurnFailureKind.ts` 新增,`DirectTurnFailure.ts` 的 `kind` 由 `string` 收窄成 union - 受影响断言(`direct_thread_manager` / `direct_turn_accept` / `direct_thread_wire` / `codex_app_server`)改成比较枚举变体