Function migrate_log 

pub fn migrate_log(
    log: &mut ObservationLog,
    sz: &Standardizer,
    names: &[String],
    nyquist: f64,
) -> usize

Rewrite a schema-1 log into the current schema, in place.

sz must be the standardizer the log was written under (the one the profile carries) and names the φ names of the stimulus the log was recorded under — v1_names for every schema-1 log, since raw-φ logging and the v2 stimulus both postdate schema 1. Returns how many observations were migrated; observations already in the current schema are left alone, and the whole thing is a no-op if the standardizer’s dimension doesn’t match schema 1 (in which case we genuinely cannot recover the raw values, and pretending otherwise would corrupt the profile).