Use commander preAction hook for setMode

Hooks are new to commander v8. We can use hooks to ensure that `setMode`
is called before every command is invoked.

node_modules/commander/esm.mjs

@@ -0,0 +1,15 @@
+import commander from './index.js';
+
+// wrapper to provide named exports for ESM.
+export const {
+  program,
+  createCommand,
+  createArgument,
+  createOption,
+  CommanderError,
+  InvalidArgumentError,
+  Command,
+  Argument,
+  Option,
+  Help
+} = commander;