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>

storybook/stories/Button.stories.tsx

@@ -0,0 +1,79 @@
+import type { Meta, StoryObj } from "@storybook/react";
+import { Button } from "@managemate/react";
+
+const meta = {
+  title: "Forms/Button",
+  component: Button,
+  tags: ["autodocs"],
+  parameters: {
+    docs: {
+      description: {
+        component:
+          "Bouton DSMMG avec variants Material 3 / Fluent. Pill par défaut. Tous les états (default, hover, active, focus-visible, disabled, loading) sont stylés. Touch target 44×44 garanti pour `icon-only`.",
+      },
+    },
+  },
+  argTypes: {
+    variant: {
+      control: "select",
+      options: ["primary", "tonal", "secondary", "tertiary", "ghost", "elevated", "danger", "success"],
+    },
+    size: { control: "select", options: ["xs", "sm", "md", "lg", "xl"] },
+    loading: { control: "boolean" },
+    disabled: { control: "boolean" },
+    block: { control: "boolean" },
+  },
+  args: { children: "Continuer", variant: "primary", size: "md" },
+} satisfies Meta<typeof Button>;
+
+export default meta;
+type Story = StoryObj<typeof meta>;
+
+export const Primary: Story = {};
+
+export const Tonal: Story = { args: { variant: "tonal" } };
+export const Secondary: Story = { args: { variant: "secondary" } };
+export const Tertiary: Story = { args: { variant: "tertiary" } };
+export const Ghost: Story = { args: { variant: "ghost" } };
+export const Elevated: Story = { args: { variant: "elevated" } };
+export const Danger: Story = { args: { variant: "danger", children: "Supprimer" } };
+export const Success: Story = { args: { variant: "success", children: "Valider" } };
+
+export const Loading: Story = { args: { loading: true } };
+export const Disabled: Story = { args: { disabled: true } };
+export const Block: Story = { args: { block: true } };
+
+export const WithIcon: Story = {
+  args: { icon: "arrow-right-line", iconPosition: "right" },
+};
+
+export const IconOnly: Story = {
+  args: { icon: "settings-3-line", "aria-label": "Paramètres", children: undefined },
+};
+
+export const AllSizes: Story = {
+  render: (args) => (
+    <div style={{ display: "flex", gap: 12, alignItems: "center" }}>
+      <Button {...args} size="xs">XS</Button>
+      <Button {...args} size="sm">Small</Button>
+      <Button {...args} size="md">Medium</Button>
+      <Button {...args} size="lg">Large</Button>
+      <Button {...args} size="xl">Extra</Button>
+    </div>
+  ),
+};
+
+export const AllVariants: Story = {
+  render: () => (
+    <div style={{ display: "flex", gap: 12, flexWrap: "wrap" }}>
+      <Button variant="primary">Primary</Button>
+      <Button variant="tonal">Tonal</Button>
+      <Button variant="secondary">Secondary</Button>
+      <Button variant="tertiary">Tertiary</Button>
+      <Button variant="ghost">Ghost</Button>
+      <Button variant="elevated">Elevated</Button>
+      <Button variant="danger">Danger</Button>
+      <Button variant="success">Success</Button>
+    </div>
+  ),
+};