These functions manage the turn history of the active LLM conversation so that sessions can be saved, restored, listed, or reset.
save_chat() snapshots the current conversation under a name.
restore_chat() replaces the current conversation with a saved snapshot.
list_chats() returns the names of all saved snapshots.
reset_chat() clears the current conversation turn history.
save_chat() and reset_chat() return invisible(NULL).
restore_chat() returns invisible(NULL). list_chats() returns a
character vector of snapshot names (or an empty vector if none exist).