Fix case-app initialization

[Gedochao]

This fixes the scala-packager CLI failing on init with:

[error] java.lang.NullPointerException: Cannot invoke "caseapp.core.help.Help.progName()" because the return value of "caseapp.core.app.CaseApp.help()" is null
[error] 	at caseapp.core.app.CaseApp.name(CaseApp.scala:[14](https://github.com/VirtusLab/scala-packager/actions/runs/11972808082/job/33380448142?pr=195#step:6:15))
[error] 	at caseapp.core.app.Command.names(Command.scala:9)
[error] 	at caseapp.core.commandparser.RuntimeCommandParser$.$anonfun$commandMap$1(RuntimeCommandParser.scala:30)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:294)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:79)
[error] 	at caseapp.core.commandparser.RuntimeCommandParser$.commandMap(RuntimeCommandParser.scala:29)
[error] 	at caseapp.core.commandparser.RuntimeCommandParser$.parse(RuntimeCommandParser.scala:47)
[error] 	at caseapp.core.app.CommandsEntryPoint.main(CommandsEntryPoint.scala:369)
[error] 	at packager.cli.PackagerCli.main(PackagerCli.scala)
[error] 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
[error] 	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.base/java.lang.reflect.Method.invoke(Method.java:569)

We'll also run the CLI straight from SBT on the CI as a sanity check (the actual integration checks are in the Scala CLI repo, but we do need a sanity check here).