feat(chart): add @hm-design/chart package with Bar, Line, Donut, Pie, Radar, Area and Radial charts

- new workspace package packages/chart (shadcn/ui Chart + Recharts, HM Theme tokens), examples entry with sample data
- Storybook Chart group (src/chart), consumer example (examples/chart), build:chart / build:chart-example scripts
- README rewritten as the AI usage guide (install, CSS wiring, chart selection, data rules, verification)
- docs: package count/list, Submodule guide (chart workspace, React dedupe), shared AI_GUIDE row, MAINTAINING, story inventory

src/chart/line-chart.stories.tsx

@@ -0,0 +1,50 @@
+import type { Meta, StoryObj } from "@storybook/react-vite"
+import {
+  LineCurveDotLabelExample,
+  LineCurveExample,
+  LineStepDotLabelExample,
+  LineStepExample,
+  LineStraightColorLabelExample,
+  LineStraightExample,
+} from "@hm-design/chart/examples"
+import { StoryPage, StoryPageHeader, StorySection } from "@/components/story-page"
+
+// Sample data only. All six examples share one data set and axis range, so connection styles compare directly: curve, straight
+// and step, each as a plain line (left) and with Dots and value labels (right).
+const meta = {
+  title: "Chart/Line Chart",
+  parameters: { layout: "fullscreen", controls: { disable: true } },
+} satisfies Meta
+export default meta
+type Story = StoryObj<typeof meta>
+
+export const Line: Story = {
+  name: "Line Chart",
+  render: () => (
+    <StoryPage>
+      <StoryPageHeader title="Line Chart" />
+      {/* Same grid as Bar Chart: two per row from 1024px, one below. Source order is the mobile order; desktop reads row by row:
+          Curve | Curve + labels, Straight | Straight + colored labels, Step | Step + labels. */}
+      <div className="grid grid-cols-1 gap-x-6 lg:auto-rows-fr lg:grid-cols-2 *:flex *:min-w-0 *:flex-col [&_.sb-page-section-body]:flex-1">
+        <StorySection title="Curve">
+          <LineCurveExample />
+        </StorySection>
+        <StorySection title="Curve · Dot + Label">
+          <LineCurveDotLabelExample />
+        </StorySection>
+        <StorySection title="Straight">
+          <LineStraightExample />
+        </StorySection>
+        <StorySection title="Straight · Color Dot + Label">
+          <LineStraightColorLabelExample />
+        </StorySection>
+        <StorySection title="Step">
+          <LineStepExample />
+        </StorySection>
+        <StorySection title="Step · Dot + Label">
+          <LineStepDotLabelExample />
+        </StorySection>
+      </div>
+    </StoryPage>
+  ),
+}