GET /api/skill-gaps aggregates skill_usage rows with found=false by
skill, agent, and task category. Hits are returned for the same key so a
miss rate needs no second query; hit-only skills are excluded. The source
rows already existed: a miss is written when the model names a skill the
platform does not provide.
This is the evidence-backed capability backlog, not an auto-fixer: it
creates no skill and changes no prompt. Motivated by the harness and
skill-evolution sections of awesome-rsi (lobehub).
