Trigger finding enrichment for a skill

Starts the finding-enrichment Temporal workflow for a skill named by skillId, skillVersionId, tileVersionSkillId, or explicit source coordinates. Findings default to those from the skill's latest security review; pass findings to enrich an explicit set instead. Returns the run handle to poll. Returns 422 when the findings derived from the skill's latest review are not enrichable (an explicit findings payload bypasses this check).