Make Conversation a pointer refernece on Message

Instead of a value, which lead some odd handling of conversation
references.

Also fixed some formatting and removed an unnecessary (and probably
broken) setting of ConversationID in a call to
`cmdutil.HandleConversationReply`

pkg/tui/views/chat/update.go

@@ -173,7 +173,7 @@ func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
 		m.updateContent()
 	case msgMessageCloned:
 		if msg.Parent == nil {
-			m.conversation = &msg.Conversation
+			m.conversation = msg.Conversation
 			m.rootMessages = append(m.rootMessages, *msg)
 		}
 		cmds = append(cmds, m.loadConversationMessages())