Function cosine_similarity_budgeted 

pub fn cosine_similarity_budgeted(
    a: &[f32],
    b: &[f32],
    budget: Duration,
) -> (f32, bool)

Time-budgeted cosine similarity.

Same as cosine_similarity but aborts and returns (0.0, true) if the computation exceeds budget. Checks every 128 element pairs.