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/slider.tsx

@@ -0,0 +1,61 @@
+import * as React from "react";
+import * as SliderPrimitive from "@radix-ui/react-slider";
+
+import { cn } from "@/lib/utils";
+
+function Slider({
+  className,
+  defaultValue,
+  value,
+  min = 0,
+  max = 100,
+  ...props
+}: React.ComponentProps<typeof SliderPrimitive.Root>) {
+  const _values = React.useMemo(
+    () =>
+      Array.isArray(value)
+        ? value
+        : Array.isArray(defaultValue)
+          ? defaultValue
+          : [min, max],
+    [value, defaultValue, min, max]
+  );
+
+  return (
+    <SliderPrimitive.Root
+      data-slot="slider"
+      defaultValue={defaultValue}
+      value={value}
+      min={min}
+      max={max}
+      className={cn(
+        "relative flex w-full touch-none items-center select-none data-[disabled]:opacity-50 data-[orientation=vertical]:h-full data-[orientation=vertical]:min-h-44 data-[orientation=vertical]:w-auto data-[orientation=vertical]:flex-col",
+        className
+      )}
+      {...props}
+    >
+      <SliderPrimitive.Track
+        data-slot="slider-track"
+        className={cn(
+          "bg-muted relative grow overflow-hidden rounded-full data-[orientation=horizontal]:h-1.5 data-[orientation=horizontal]:w-full data-[orientation=vertical]:h-full data-[orientation=vertical]:w-1.5"
+        )}
+      >
+        <SliderPrimitive.Range
+          data-slot="slider-range"
+          className={cn(
+            "bg-primary absolute data-[orientation=horizontal]:h-full data-[orientation=vertical]:w-full"
+          )}
+        />
+      </SliderPrimitive.Track>
+      {Array.from({ length: _values.length }, (_, index) => (
+        <SliderPrimitive.Thumb
+          data-slot="slider-thumb"
+          key={index}
+          className="border-primary ring-ring/50 block size-4 shrink-0 rounded-full border bg-white shadow-sm transition-[color,box-shadow] hover:ring-4 focus-visible:ring-4 focus-visible:outline-hidden disabled:pointer-events-none disabled:opacity-50"
+        />
+      ))}
+    </SliderPrimitive.Root>
+  );
+}
+
+export { Slider };