feat(platform): add the Paper design system and isolated workbench
Adds the new Platform design system and a standalone Next.js workbench under apps/sim/platform. The library covers 608 Paper masters with evidence of a Platform use. It pairs native interactive controls with typed structural recipes and centralizes typography, color, materials, icons and responsive sizing.
The workbench supports light and dark themes, empty organizations, populated workspaces and long content. Repeated rows, attachment batches and plots take typed records. Chart marks, labels, totals and tooltips follow the same data even when its length differs from the Paper specimen. Sample data loads only with SIM_PLATFORM_FIXTURES=1. Run SIM_PLATFORM_FIXTURES=1 bun run --cwd apps/sim dev:platform and open port 3100.
The implementation skill and scoped agent instructions define how to promote a feature component, retire a variant and verify a change against Paper. CI checks ownership, styling boundaries, token references and supported variants, including unused variants behind unreachable branches and inherited style props. Browser tests exercise keyboard interaction, selection, nested popovers and dialogs, fixture isolation, variable-length collections and charts, scrolling, type scaling and responsive layouts.
Validation includes the production build, Playwright, repository lint, TypeScript, the audit suite and the full repository test suite. The 26-case production suite also requests all 608 catalog selections through the workbench. Dashboard table coverage includes number formatting, zero versus missing values and six-, four- and three-column layouts.
The main-view and modal value pickers now share the same Paper popup surface and item recipe. Unstyled Base UI primitives own selection, filtering, keyboard navigation, hover submenus and collision-aware placement. Focus preserves the resting paint across Platform controls. The design audit enforces the rule and browser tests exercise the actual inputs, cascade and dialog layers.