Function is_interactive 

pub fn is_interactive() -> bool

Returns true when stdin is a terminal (interactive), false otherwise (e.g. a pipe or redirected file – the common CI case).

Centralizes the TTY check so add and init share one predicate instead of each duplicating IsTerminal. Thin wrapper over std::io::IsTerminal::is_terminal, no state – callers inject a bool test double rather than testing this directly, since the OS determines the trait’s return value, not Rust code. Non-interactive-path coverage lives in cli_tests.rs’s test_add_non_interactive_via_pipe (pipes stdin, asserts callisto add skips the TTY wizard).