Function muddy_child_knows 

pub fn muddy_child_knows(num_muddy: u32, round: u32) -> bool

The Muddy Children deduction: after the public announcement “at least one is muddy”, each silent round eliminates a hypothesis; a muddy child deduces it is muddy exactly at round == num_muddy (1-indexed). Shows how common knowledge + iterated “I don’t know” produces knowledge. Returns whether a muddy child KNOWS its own state at round.