Zero-dependency, tolerant XML reader (elements/attrs/text/comments/prolog/ CDATA/entities; <style> read as raw text) producing a generic element tree. The normalizer folds d2/graphviz's class-based <style> rules into inline presentation attributes — cascade presentation-attr < tag < class < style — then drops <style>/class/style, so the painter only ever sees inline attrs (D-103). Flutter-free, covered by dart test (26 cases). No user-visible behaviour yet. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>