cli: remove app index.ts compatibility shim in next major version (v12)

Tracking issue for a TODO found in `packages/cli/src/cli/commands/app/index.ts`:

```ts
// @todo - remove in next major version v12
```

Remove this backward-compatibility code in the next major (v12) release.

Open packages/cli/src/cli/commands/app/index.ts and locate the compatibility code marked with the v12 TODO. Review how the app command currently uses that backward-compatibility path, then remove it for the v12 release. Done means the obsolete shim is gone and the app command remains correctly wired.

Written by the indexing model from the issue text.