Resume all chats naturally when opening/updating GHCP

The current way of resuming chats may not resume sessions accurately and is wasting resources.

We currently send a prompt : "_Continue from where you left off._" after reopening GHCP instead of chat sessions resuming naturally.

We are burning tokens and compute for no reason right now and this should be reviewed asap.

首先追踪应用重新打开或更新时使用的 GHCP 聊天会话恢复流程，包括发送 "Continue from where you left off" 提示的位置。将该行为与重新打开时可用的会话状态进行比较。当聊天能够自然恢复而无需额外提示，并且消除了不必要的 token 和计算资源使用时，即视为完成。

由索引模型根据 Issue 内容生成。