Replace Tailwind utility soup across admin templates with semantic
CSS classes. Add layout primitives (stack, row, cluster, grid),
extract JS transition helpers into transitions.css, and refactor
core_components, layouts, settings, newsletter, order_show, providers,
and theme editor templates.
Utility occurrences reduced from 290+ to 127 across admin files.
All 1679 tests pass.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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