Persist current tree in navigation/shared conversations

[nsarrazin]

Would be nice to be able to keep the current tree in view when refreshing, or sharing a conversation. Currently it gets reset to the first children at every branching.

I think the navigation persistance could be done using sveltekit snapshots. We just need a way to represent the current subtree and store it. We could also store this representation when sharing a conversation, to allow sharing a specific subtree.

[kramosss]

Hi, I'm working on this.