Fix CLI version flag and update prompt handling

[BigGig17]

Context

This fixes the CLI version flag so help advertises -v, --version and dx -v prints the current package version without running the update check. It also keeps version-update prompts out of metadata-only invocations like --help and routes the interactive update selector to stderr so the choices remain visible when stdout is captured.

QA

• Verify dx -v prints only the current version and does not show an update prompt.
• Check dx --help lists -v, --version and does not list -V, --version.
• Exercise a normal command with a newer CLI version available and confirm the update choices render visibly.

Links

slack message