Function to_command 

pub fn to_command(
    recommendations: &Recommendations,
    input: &Path,
    time_field: &str,
) -> String

Convert recommendations to an stt-build command line.

NON-LOSSY advisor advice is appended (flag + value, in advisor order) so the pasteable command carries the reversible byte-level/semantic levers. LOSSY advice (quantization, budgets) NEVER joins the command — it degrades data and stays a per-dataset opt-in the user must add by hand.