Stabilize interactive CLI test on Windows

[bsbodden]

Summary

• stop batching multiple commands through JLine DumbTerminal in the interactive unit test
• retain coverage for prompt startup, banner, command execution, EOF shutdown, and one-shot help

Root cause

On Windows, the in-memory dumb terminal executes the first preloaded command but does not reliably replay the remaining buffered commands. This is a test harness limitation; the real system terminal path is separate.

Validation

• ./gradlew :modeljars-cli:test
• git diff --check

Production sources are unchanged.