Add harness workflow and Material showcase design system

docs/exec-plans/2026-03-23-material-you-convergence.md

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+# Material You Convergence
+
+- Status: `completed`
+- Owner: `codex`
+- Date: `2026-03-23`
+
+## Goal
+
+Converge Cadence UI from a multi-skin showcase system into a single Material You inspired
+design language with dynamic seed-color theming, tonal surfaces, large-radius component
+defaults, and one consistent motion vocabulary plus a reduced/static accessibility override.
+
+## Scope
+
+- In scope:
+  - replace the current `minimal / glass / pixel` skin contract with a single `material` skin
+  - shift token defaults toward Material You roles and typography
+  - introduce runtime dynamic color generation from a seed color
+  - retune component surface variables around tonal containers instead of decorative skins
+  - update Storybook preview and foundation stories away from multi-skin demos
+  - update package and contract tests that exercise the public runtime styling API
+  - promote `DESIGN.md` into the repository system of record
+  - push the visual language further toward a showcase-grade Material presentation
+- Out of scope:
+  - full wallpaper extraction from host operating systems
+  - dark theme parity for every token role in this first convergence slice
+  - a full component-by-component redesign of every docs story
+
+## Constraints
+
+- Keep the existing package import structure working for `@ai-ui/ui` and `@ai-ui/tokens`.
+- Preserve the reduced/static motion accessibility mode.
+- Prefer aliasing and runtime helpers over a sweeping component API rewrite.
+- Record the direction change explicitly instead of silently continuing the multi-skin RFC.
+
+## Affected Surfaces
+
+- `packages/tokens/src/*`
+- `packages/ui/src/lib/*`
+- `packages/ui/src/skins.css`
+- `packages/ui/src/styles.css`
+- `apps/docs/.storybook/preview.ts`
+- `apps/docs/src/*.stories.tsx`
+- `DESIGN.md`
+- `AGENTS.md`
+- `README.md`
+- `tests/package-consumer/*`
+- `docs/exec-plans/*`
+
+## Plan
+
+1. Replace the style runtime contract with Material-centric theme and motion semantics.
+2. Add a seed-color palette generator and map generated roles onto existing component tokens.
+3. Collapse skin CSS to a single Material skin and retune shared component variables.
+4. Update Storybook docs to demonstrate dynamic color, tonal surfaces, and the single motion language.
+5. Promote `DESIGN.md` into the repository's official design system of record.
+6. Push the showcase styling and motion layer until the docs feel closer to a Material launch demo.
+7. Run focused validation on package contracts, docs build, and consumer smoke.
+
+## Validation
+
+- `pnpm test`
+- `pnpm typecheck`
+- `pnpm build:docs`
+- `pnpm test:package:consumer`
+
+## Orchestration Task Sketch
+
+- `T1`: token/runtime contract shift
+- `T2`: shared component surface restyle
+- `T3`: docs and consumer validation updates
+
+## Status Log
+
+- `2026-03-23 14:18` started convergence plan after product direction changed from multi-skin showcase to Material You
+- `2026-03-23 16:15` promoted `DESIGN.md` to the active design-system source of truth and started a second-pass visual polish toward a more animated Material showcase
+- `2026-03-23 16:58` completed the second-pass polish across tokens, shared skin variables, Storybook showcase pages, and package-consumer validation