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/cmd/clone.go

@@ -27,7 +27,7 @@ func CloneCmd(ctx *lmcli.Context) *cobra.Command {
 				return err
 			}
 
-			clone, messageCnt, err := ctx.Store.CloneConversation(*toClone)
+			clone, messageCnt, err := ctx.Conversations.CloneConversation(*toClone)
 			if err != nil {
 				return fmt.Errorf("Failed to clone conversation: %v", err)
 			}
@@ -40,7 +40,7 @@ func CloneCmd(ctx *lmcli.Context) *cobra.Command {
 			if len(args) != 0 {
 				return nil, compMode
 			}
-			return ctx.Store.ConversationShortNameCompletions(toComplete), compMode
+			return ctx.Conversations.ConversationShortNameCompletions(toComplete), compMode
 		},
 	}
 	return cmd