Tweaks/cleanups to conversation management in tui

- Pass around message/conversation values instead of pointers where it
makes more sense, and store values instead of pointers in the globally
(within the TUI) shared `App` (pointers provide no utility here).

- Split conversation persistence into separate conversation/message
  saving stages

pkg/tui/views/chat/update.go

@@ -75,7 +75,7 @@ func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
 		m.rebuildMessageCache()
 		m.updateContent()
 
-		if m.App.Conversation != nil && m.App.Conversation.ID > 0 {
+		if m.App.Conversation.ID > 0 {
 			// (re)load conversation contents
 			cmds = append(cmds, m.loadConversationMessages())
 		}
@@ -133,7 +133,7 @@ func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
 	case msgChatResponse:
 		m.state = idle
 
-		reply := (*conversation.Message)(msg)
+		reply := conversation.Message(msg)
 		reply.Content = strings.TrimSpace(reply.Content)
 
 		last := len(m.App.Messages) - 1
@@ -142,16 +142,15 @@ func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
 		}
 
 		if m.App.Messages[last].Role.IsAssistant() {
-			// TODO: handle continuations gracefully - some models support them well, others fail horribly.
-			m.setMessage(last, *reply)
+			// TODO: handle continuations gracefully - only some models support them
+			m.setMessage(last, reply)
 		} else {
-			m.addMessage(*reply)
+			m.addMessage(reply)
 		}
 
-		switch reply.Role {
-		case api.MessageRoleToolCall:
+		if reply.Role == api.MessageRoleToolCall {
 			// TODO: user confirmation before execution
-			// m.state = waitingForConfirmation
+			// m.state = confirmToolUse
 			cmds = append(cmds, m.executeToolCalls(reply.ToolCalls))
 		}
 
@@ -159,11 +158,9 @@ func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
 			cmds = append(cmds, m.persistConversation())
 		}
 
-		if m.App.Conversation.Title == "" {
+		if m.App.Conversation.Title == "" && len(m.App.Messages) > 0 {
 			cmds = append(cmds, m.generateConversationTitle())
 		}
-
-		m.updateContent()
 	case msgChatResponseCanceled:
 		m.state = idle
 		m.updateContent()
@@ -194,8 +191,8 @@ func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
 	case msgConversationTitleGenerated:
 		title := string(msg)
 		m.App.Conversation.Title = title
-		if m.persistence {
-			cmds = append(cmds, m.updateConversationTitle(m.App.Conversation))
+		if m.persistence && m.App.Conversation.ID > 0 {
+			cmds = append(cmds, m.persistConversation())
 		}
 	case cursor.BlinkMsg:
 		if m.state == pendingResponse {
@@ -205,14 +202,13 @@ func (m *Model) Update(msg tea.Msg) (shared.ViewModel, tea.Cmd) {
 			m.updateContent()
 		}
 	case msgConversationPersisted:
-		m.App.Conversation = msg.conversation
-		m.App.Messages = msg.messages
+		m.App.Conversation = conversation.Conversation(msg)
+		cmds = append(cmds, m.persistMessages())
+	case msgMessagesPersisted:
+		m.App.Messages = msg
 		m.rebuildMessageCache()
 		m.updateContent()
 	case msgMessageCloned:
-		if msg.Parent == nil {
-			m.App.Conversation = msg.Conversation
-		}
 		cmds = append(cmds, m.loadConversationMessages())
 	case msgSelectedRootCycled, msgSelectedReplyCycled, msgMessageUpdated:
 		cmds = append(cmds, m.loadConversationMessages())