Selects the right chart type and visualization library for React/Next.js (web) and Expo/React Native (mobile) data visualization tasks, then applies accessibility and anti-pattern guardrails. Maps data shape and intent (comparison, composition, distribution, relationship, evolution, flow, geographic, hierarchical) to a recommended chart, then to a recommended library based on platform, dataset size, and design system. Defers cross-cutting UI concerns (contrast, touch targets, typography, copy) to the `ux` skill rather than restating them. Triggers on: "what chart should I use", "visualize this data", "build a chart", "build a dashboard", "data visualization", "pick a chart library", "graph this", "/charting".