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

packages/chart/src/components/text-fit.ts

@@ -0,0 +1,18 @@
+// SVG text cannot ellipsize itself, so labels are measured by estimate (full-width glyphs 1em, others ~0.6em) and shortened here.
+
+export function textWidth(text: string, fontSize: number) {
+  let width = 0
+  for (const char of text) width += (char.codePointAt(0) ?? 0) > 0x2e7f ? fontSize : fontSize * 0.6
+  return width
+}
+
+/** The longest start of `text` plus an ellipsis that fits `maxWidth`; "" when not even one character fits. */
+export function fitText(text: string, maxWidth: number, fontSize: number) {
+  if (textWidth(text, fontSize) <= maxWidth) return text
+  const chars = [...text]
+  for (let count = chars.length - 1; count > 0; count -= 1) {
+    const candidate = `${chars.slice(0, count).join("").trimEnd()}…`
+    if (textWidth(candidate, fontSize) <= maxWidth) return candidate
+  }
+  return ""
+}