fix(tui): optimistic rendering (#692)

packages/tui/internal/components/chat/messages.go

@@ -68,11 +68,9 @@ func (m *messagesComponent) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.selectedPart = -1
 		return m, nil
 	case app.OptimisticMessageAddedMsg:
-		m.renderView(m.width)
-		if m.tail {
-			m.viewport.GotoBottom()
-		}
-		return m, nil
+		m.tail = true
+		m.rendering = true
+		return m, m.Reload()
 	case dialog.ThemeSelectedMsg:
 		m.cache.Clear()
 		m.rendering = true