Conventions for creating, modifying, and reviewing production-faithful Storybook stories in the Phoenix frontend (js/app/stories, js/app/.storybook). Covers sidebar taxonomy and titles, the tag vocabulary, entry shape, option grids, component audits, overlays, toasts, themes, domain stories, and Storybook configuration. Use whenever touching `.stories.*` or story `.mdx` files, story fixtures, decorators, helpers in `stories/utils`, thumbnails, `.storybook/` configuration, or a frontend change that adds, changes, moves, or removes stories — including small or mechanical story edits and PR reviews that touch stories.