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/model/model.go

@@ -16,7 +16,7 @@ import (
 type AppModel struct {
 	Ctx           *lmcli.Context
 	Conversations conversation.ConversationList
-	Conversation  *conversation.Conversation
+	Conversation  conversation.Conversation
 	Messages      []conversation.Message
 	Model         string
 	ProviderName  string
@@ -27,12 +27,13 @@ type AppModel struct {
 func NewAppModel(ctx *lmcli.Context, initialConversation *conversation.Conversation) *AppModel {
 	app := &AppModel{
 		Ctx:          ctx,
-		Conversation: initialConversation,
 		Model:        *ctx.Config.Defaults.Model,
 	}
 
 	if initialConversation == nil {
 		app.NewConversation()
+	} else {
+
 	}
 
 	model, provider, _, _ := ctx.GetModelProvider(*ctx.Config.Defaults.Model, "")
@@ -61,7 +62,7 @@ const (
 )
 
 func (m *AppModel) ClearConversation() {
-	m.Conversation = nil
+	m.Conversation = conversation.Conversation{}
 	m.Messages = []conversation.Message{}
 }
 
@@ -96,10 +97,6 @@ func (a *AppModel) GenerateConversationTitle(messages []conversation.Message) (s
 	return cmdutil.GenerateTitle(a.Ctx, messages)
 }
 
-func (a *AppModel) UpdateConversationTitle(conversation *conversation.Conversation) error {
-	return a.Ctx.Conversations.UpdateConversation(conversation)
-}
-
 func (a *AppModel) CloneMessage(message conversation.Message, selected bool) (*conversation.Message, error) {
 	msg, _, err := a.Ctx.Conversations.CloneBranch(message)
 	if err != nil {
@@ -182,33 +179,54 @@ func (a *AppModel) CycleSelectedReply(message *conversation.Message, dir Message
 	return nextReply, nil
 }
 
-func (a *AppModel) PersistConversation(conversation *conversation.Conversation, messages []conversation.Message) (*conversation.Conversation, []conversation.Message, error) {
-	var err error
-	if conversation == nil || conversation.ID == 0 {
-		conversation, messages, err = a.Ctx.Conversations.StartConversation(messages...)
-		if err != nil {
-			return nil, nil, fmt.Errorf("Could not start new conversation: %v", err)
-		}
-		return conversation, messages, nil
-	}
-
-	for i := range messages {
-		if messages[i].ID > 0 {
-			err := a.Ctx.Conversations.UpdateMessage(&messages[i])
+func (a *AppModel) PersistMessages() ([]conversation.Message, error) {
+	messages := make([]conversation.Message, len(a.Messages))
+	for i, m := range a.Messages {
+		if i == 0 && m.ID == 0 {
+			m.Conversation = &a.Conversation
+			m, err := a.Ctx.Conversations.SaveMessage(m)
 			if err != nil {
-				return nil, nil, err
+				return nil, fmt.Errorf("Could not create first message %d: %v", a.Messages[i].ID, err)
 			}
+			messages[i] = *m
+			// let's set the conversation root message(s), as this is the first message
+			m.Conversation.RootMessages = []conversation.Message{*m}
+			m.Conversation.SelectedRoot = &m.Conversation.RootMessages[0]
+			a.Ctx.Conversations.UpdateConversation(m.Conversation)
+		} else if m.ID > 0 {
+			// Existing message, update it
+			err := a.Ctx.Conversations.UpdateMessage(&m)
+			if err != nil {
+				return nil, fmt.Errorf("Could not update message %d: %v", a.Messages[i].ID, err)
+			}
+			messages[i] = m
 		} else if i > 0 {
-			saved, err := a.Ctx.Conversations.Reply(&messages[i-1], messages[i])
+			// New message, reply to previous
+			replies, err := a.Ctx.Conversations.Reply(&messages[i-1], m)
 			if err != nil {
-				return nil, nil, err
+				return nil, fmt.Errorf("Could not reply with new message: %v", err)
 			}
-			messages[i] = saved[0]
+			messages[i] = replies[0]
 		} else {
-			return nil, nil, fmt.Errorf("Error: no messages to reply to")
+			return nil, fmt.Errorf("No messages to reply to (this is a bug)")
 		}
 	}
-	return conversation, messages, nil
+	return messages, nil
+}
+
+func (a *AppModel) PersistConversation() (conversation.Conversation, error) {
+	conv := a.Conversation
+	var err error
+	if a.Conversation.ID > 0 {
+		err = a.Ctx.Conversations.UpdateConversation(&conv)
+	} else {
+		c, e := a.Ctx.Conversations.CreateConversation("")
+		err = e
+		if e == nil && c != nil {
+		  conv = *c
+		}
+	}
+	return conv, err
 }
 
 func (a *AppModel) ExecuteToolCalls(toolCalls []api.ToolCall) ([]api.ToolResult, error) {