修复失败刷新恢复与长会话恢复入口

[2002yy]

范围

仅修复 Study Agent 主学习工作台的恢复闭环。Closes #91。

修复

• 最新 turn 为 failed 时，刷新后恢复为 retry-only 状态
• 零 token 失败不显示“从断点继续”，不伪造部分回答
• 中断 turn 仍可从原 turn 断点续写
• 恢复卡在 conversation flex 序列中固定到消息尾部，并在当前 viewport 内 sticky 可见
• failed-before-reply 不显示“部分回答已保留/复制”快捷条
• 不改变后端 failed / interrupted durable status
• 不推进 committed learning state，不触碰 Provider、群聊、新闻、工具或 claim UI

回归

• 单元测试覆盖 latest failed、interrupted、completed/abandoned 后不误恢复
• 新增长历史恢复可见性 fixture，覆盖 desktop、390×844、360×520
• real-stack 覆盖 zero-token failure -> reload -> retry -> parent superseded + one completed child
• 保留 partial interruption -> reload -> same-turn continuation

合并门禁

保持 Draft，等待完整 pytest、RAG K1、Ruff、detect-secrets、mypy、frontend、browser journeys 与 real-stack 全绿。

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep failed continuations retry-only

When continuing an interrupted turn fails before emitting another token, ChatService.fail_turn preserves the previous partial reply but records the turn as failed. After reload, this reply-only check consequently exposes “从断点继续”; however, ChatService._validate_turn_command rejects continuation targets whose status is not interrupted, so clicking it only produces an error. Carry the restored turn status into the recovery state and offer continuation only for interrupted turns, while leaving failed turns retry-only.

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