feat(frontend): add Front/ — Vite/React frontend with backend pipeline integration

Mirror of design_agent_front/design-agent/ for shipping alongside backend.

Vite plugin (vitePluginPhaseZApi) endpoints :
  - POST /api/run   — spawn `python -m src.phase_z2_pipeline` with overrides
  - GET  /api/sample-mdx?mdx=03/04/05 — fixed sample MDX
  - GET  /frame-preview/{n} — figma preview thumbnails
  - GET  /data/runs/{run_id}/{path} — pipeline artifacts (final.html, step*.json, ...)

Env toggle forward (보고용) :
  PHASE_Z_ALLOW_RESTRUCTURE / PHASE_Z_ALLOW_REJECT / PHASE_Z_MAX_RANK=32

Components :
  - LeftMdxPanel (03/04/05 fix list + section tree)
  - SlideCanvas (iframe + slideOverrideCss prop for inline CSS inject)
  - FramePanel (label priority + confidence sort)
  - LayoutPanel

README with mermaid diagrams covering the 5-step demo flow.
node_modules / dist / .manus-logs / .env excluded via .gitignore.

Front/client/src/components/ui/radio-group.tsx

@@ -0,0 +1,43 @@
+import * as React from "react";
+import * as RadioGroupPrimitive from "@radix-ui/react-radio-group";
+import { CircleIcon } from "lucide-react";
+
+import { cn } from "@/lib/utils";
+
+function RadioGroup({
+  className,
+  ...props
+}: React.ComponentProps<typeof RadioGroupPrimitive.Root>) {
+  return (
+    <RadioGroupPrimitive.Root
+      data-slot="radio-group"
+      className={cn("grid gap-3", className)}
+      {...props}
+    />
+  );
+}
+
+function RadioGroupItem({
+  className,
+  ...props
+}: React.ComponentProps<typeof RadioGroupPrimitive.Item>) {
+  return (
+    <RadioGroupPrimitive.Item
+      data-slot="radio-group-item"
+      className={cn(
+        "border-input text-primary focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 aspect-square size-4 shrink-0 rounded-full border shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50",
+        className
+      )}
+      {...props}
+    >
+      <RadioGroupPrimitive.Indicator
+        data-slot="radio-group-indicator"
+        className="relative flex items-center justify-center"
+      >
+        <CircleIcon className="fill-primary absolute top-1/2 left-1/2 size-2 -translate-x-1/2 -translate-y-1/2" />
+      </RadioGroupPrimitive.Indicator>
+    </RadioGroupPrimitive.Item>
+  );
+}
+
+export { RadioGroup, RadioGroupItem };