Add `quiet: bool` to `Human` variant and expand `from_flags` to three args (`json`, `quiet`, `plain_env`). Update `handle`/`handle_human` accordingly; add four targeted unit tests (TDD). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add `quiet: bool` to `Human` variant and expand `from_flags` to three args (`json`, `quiet`, `plain_env`). Update `handle`/`handle_human` accordingly; add four targeted unit tests (TDD). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>