Choose which metric moves a digest may report

Product managers drown in dashboards, so an agent writes a weekly digest of what moved. The failure that kills digest agents is inventing trends, so a metric is only mentioned when it moved beyond its normal seasonal range.

Write select_digest_claims(names, current, baseline_mean, baseline_std, band_sigma): the rule your agent follows to pick what the digest may claim.

• names (list of str): the metric names.
• current (list of float): this week's value of each metric.
• baseline_mean, baseline_std (list of float): each metric's seasonal mean and standard deviation.
• band_sigma (float): how many standard deviations count as normal movement.
• Return the claims, in input order, each written "<name> up" or "<name> down".

Rules:

1. Index i in each list is one metric. Stop at the end of the shortest list.
2. If band_sigma is 0 or less: return [].
3. Skip a metric whose standard deviation is 0 or less.
4. A metric earns a claim when abs(current - mean) is strictly greater than band_sigma * std. A value exactly on the edge does not.
5. The claim is "<name> up" if the current value is above the mean, otherwise "<name> down".