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/release.yml

@@ -0,0 +1,49 @@
+name: Release
+
+on:
+  push:
+    branches: [main]
+
+concurrency:
+  group: release-${{ github.ref }}
+  cancel-in-progress: false
+
+permissions:
+  contents: write
+  pull-requests: write
+  packages: write
+
+jobs:
+  release:
+    name: Release / open changeset PR
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    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
+          registry-url: https://npm.pkg.github.com
+
+      - run: pnpm install --frozen-lockfile
+
+      - run: pnpm build
+
+      - name: Create release PR or publish
+        uses: changesets/action@v1
+        with:
+          publish: pnpm release
+          version: pnpm version-packages
+          commit: "chore(release): version packages"
+          title: "chore(release): version packages"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          NODE_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}