Workflow-only base skill for regulated-domain classification. Defines the three-state contract (clean / conservative-default-with-flag / refuse), the conservative-defaults principle, the citation discipline, the structured-question form, and the reviewer-attention output contract. Contains no tax content, no rates, no thresholds, no jurisdiction-specific rules. MUST be loaded alongside at least one content skill (e.g., classifying-tax-transactions) that supplies the actual rules and the current year's figures. Loading this skill alone is a configuration error and Claude must refuse to proceed.