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.

Start by tracing the GHCP chat-session resume flow used when the app is reopened or updated, including where the "Continue from where you left off" prompt is sent. Compare that behavior with the session state available at reopening. Done means chats resume naturally without the extra prompt and the unnecessary token and compute usage is eliminated.

Written by the indexing model from the issue text.