Function autorepeat_fire 

pub fn autorepeat_fire(
    is_down: bool,
    elapsed_ms_since_change: u32,
    first_delay_ms: u32,
    repeat_rate_ms: u32,
) -> bool

Autorepeat helper (legacy): when a bit is held, fires at (first_delay_ms then repeat_rate_ms). Uses modulo and can miss if jittery polls.