fix: fix chat subcommands

all of the sgpt chat subcommands (like cat, ls, rm) were broken. the
viper config was not loaded, which included the user cache dir. this
user cache dir is used to save the chat sessions.

pkg/cli/chat.go

@@ -72,6 +72,9 @@ Manage all open chat sessions - list, show, and delete chat sessions.
 		DisableFlagsInUseLine: true,
 		Args:                  cobra.NoArgs,
 		ValidArgsFunction:     cobra.NoFileCompletions,
+		PersistentPreRunE: func(_ *cobra.Command, _ []string) error {
+			return loadViperConfig(config)
+		},
 		RunE: func(cmd *cobra.Command, _ []string) error {
 			return cmd.Help()
 		},