chore: initial DSMMG v0.2 — refonte architecturale complète

Mise en place du Design System ManageMate Group v0.2 — refonte du
système de tokens (préfixe --mmg-color-*), 9 presets accent
user-themable validés WCAG AA, overlays Radix UI + Floating UI,
Storybook 8 + Vitest + axe-core en CI, doc Astro Starlight,
DESIGN.md (format google-labs-code) et exports tokens DTCG/CSS/
TS/Figma/Tailwind v3 et v4.

- 4 packages monorepo pnpm : @managemate/{tokens,css,react,icons}
- 62 composants React headless-first (Sheet, HoverCard, ContextMenu,
  Slider, ToggleGroup, AvatarGroup, UserCard, ProfileHeader,
  MetricCard, PricingCard, FeatureCard, Text/Display/Eyebrow/Lead…)
- Lint contraste WCAG : 37/37 paires AA, branché CI
- Toast pile Sonner-style avec ResizeObserver
- Theming user (9 presets) sans casser sémantique fixe
- Identité Synapse (rose #D12B6A) préservée

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,71 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  CI: true
+  HUSKY: 0
+
+jobs:
+  build:
+    name: Build, typecheck, test, a11y
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - name: Install
+        run: pnpm install --frozen-lockfile
+
+      - name: Build tokens (Style Dictionary)
+        run: pnpm --filter @managemate/tokens build
+
+      - name: Build icons
+        run: pnpm --filter @managemate/icons build
+
+      - name: Build CSS
+        run: pnpm --filter @managemate/css build
+
+      - name: Build React
+        run: pnpm --filter @managemate/react build
+
+      - name: Typecheck
+        run: pnpm --filter @managemate/react typecheck
+
+      - name: Test (Vitest + axe-core)
+        run: pnpm --filter @managemate/react test
+
+      - name: Lint contraste WCAG AA
+        run: pnpm lint:contrast
+
+      - name: Build Storybook
+        run: pnpm --filter storybook build
+
+      - name: Bundle size budget
+        run: pnpm size
+
+      - name: Upload Storybook artifact
+        if: github.event_name == 'pull_request'
+        uses: actions/upload-artifact@v4
+        with:
+          name: storybook-static
+          path: storybook/storybook-static
+          retention-days: 7