Large refactor - it compiles!

This refactor splits out all conversation concerns into a new
`conversation` package. There is now a split between `conversation` and
`api`s representation of `Message`, the latter storing the minimum
information required for interaction with LLM providers. There is
necessary conversation between the two when making LLM calls.

pkg/tui/tui.go

@@ -3,7 +3,7 @@ package tui
 import (
 	"fmt"
 
-	"git.mlow.ca/mlow/lmcli/pkg/api"
+	"git.mlow.ca/mlow/lmcli/pkg/conversation"
 	"git.mlow.ca/mlow/lmcli/pkg/lmcli"
 	"git.mlow.ca/mlow/lmcli/pkg/tui/model"
 	"git.mlow.ca/mlow/lmcli/pkg/tui/shared"
@@ -130,13 +130,13 @@ func (m *Model) View() string {
 }
 
 type LaunchOptions struct {
-	InitialConversation *api.Conversation
+	InitialConversation *conversation.Conversation
 	InitialView         shared.View
 }
 
 type LaunchOption func(*LaunchOptions)
 
-func WithInitialConversation(conv *api.Conversation) LaunchOption {
+func WithInitialConversation(conv *conversation.Conversation) LaunchOption {
 	return func(opts *LaunchOptions) {
 		opts.InitialConversation = conv
 	}