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/sheet.tsx

@@ -0,0 +1,139 @@
+"use client";
+
+import * as React from "react";
+import * as SheetPrimitive from "@radix-ui/react-dialog";
+import { XIcon } from "lucide-react";
+
+import { cn } from "@/lib/utils";
+
+function Sheet({ ...props }: React.ComponentProps<typeof SheetPrimitive.Root>) {
+  return <SheetPrimitive.Root data-slot="sheet" {...props} />;
+}
+
+function SheetTrigger({
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Trigger>) {
+  return <SheetPrimitive.Trigger data-slot="sheet-trigger" {...props} />;
+}
+
+function SheetClose({
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Close>) {
+  return <SheetPrimitive.Close data-slot="sheet-close" {...props} />;
+}
+
+function SheetPortal({
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Portal>) {
+  return <SheetPrimitive.Portal data-slot="sheet-portal" {...props} />;
+}
+
+function SheetOverlay({
+  className,
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Overlay>) {
+  return (
+    <SheetPrimitive.Overlay
+      data-slot="sheet-overlay"
+      className={cn(
+        "data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 fixed inset-0 z-50 bg-black/50",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function SheetContent({
+  className,
+  children,
+  side = "right",
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Content> & {
+  side?: "top" | "right" | "bottom" | "left";
+}) {
+  return (
+    <SheetPortal>
+      <SheetOverlay />
+      <SheetPrimitive.Content
+        data-slot="sheet-content"
+        className={cn(
+          "bg-background data-[state=open]:animate-in data-[state=closed]:animate-out fixed z-50 flex flex-col gap-4 shadow-lg transition ease-in-out data-[state=closed]:duration-300 data-[state=open]:duration-500",
+          side === "right" &&
+            "data-[state=closed]:slide-out-to-right data-[state=open]:slide-in-from-right inset-y-0 right-0 h-full w-3/4 border-l sm:max-w-sm",
+          side === "left" &&
+            "data-[state=closed]:slide-out-to-left data-[state=open]:slide-in-from-left inset-y-0 left-0 h-full w-3/4 border-r sm:max-w-sm",
+          side === "top" &&
+            "data-[state=closed]:slide-out-to-top data-[state=open]:slide-in-from-top inset-x-0 top-0 h-auto border-b",
+          side === "bottom" &&
+            "data-[state=closed]:slide-out-to-bottom data-[state=open]:slide-in-from-bottom inset-x-0 bottom-0 h-auto border-t",
+          className
+        )}
+        {...props}
+      >
+        {children}
+        <SheetPrimitive.Close className="ring-offset-background focus:ring-ring data-[state=open]:bg-secondary absolute top-4 right-4 rounded-xs opacity-70 transition-opacity hover:opacity-100 focus:ring-2 focus:ring-offset-2 focus:outline-hidden disabled:pointer-events-none">
+          <XIcon className="size-4" />
+          <span className="sr-only">Close</span>
+        </SheetPrimitive.Close>
+      </SheetPrimitive.Content>
+    </SheetPortal>
+  );
+}
+
+function SheetHeader({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="sheet-header"
+      className={cn("flex flex-col gap-1.5 p-4", className)}
+      {...props}
+    />
+  );
+}
+
+function SheetFooter({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="sheet-footer"
+      className={cn("mt-auto flex flex-col gap-2 p-4", className)}
+      {...props}
+    />
+  );
+}
+
+function SheetTitle({
+  className,
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Title>) {
+  return (
+    <SheetPrimitive.Title
+      data-slot="sheet-title"
+      className={cn("text-foreground font-semibold", className)}
+      {...props}
+    />
+  );
+}
+
+function SheetDescription({
+  className,
+  ...props
+}: React.ComponentProps<typeof SheetPrimitive.Description>) {
+  return (
+    <SheetPrimitive.Description
+      data-slot="sheet-description"
+      className={cn("text-muted-foreground text-sm", className)}
+      {...props}
+    />
+  );
+}
+
+export {
+  Sheet,
+  SheetTrigger,
+  SheetClose,
+  SheetContent,
+  SheetHeader,
+  SheetFooter,
+  SheetTitle,
+  SheetDescription,
+};