Assign area/* labels to stability / serviceability / performance issues

Follow-up from the issue-tagging rollout (see label-migration/spec.yml).

The labels stability (70 issues), serviceability (55), and performance (30) are quality attributes rather than components, so they were left untouched by the migration (not deprecated, not remapped).

Task: review the issues carrying each of these labels and assign an appropriate area/* component label, so the quality-attribute labels can eventually be retired without losing signal.