feat: React19+HMDesign shell with ported DWG/DXF viewer engine

Scaffolds the new app (Vite+React19+Tailwind v4) on HMDesign via git
submodule + npm workspace, ports src/viewer2d/* and optionsStore.ts
unchanged, and rebuilds the vanilla UI (toolbar/layers/properties/
options panels, coord readout, license dialog, load progress) as HM
Design System components. Panel drag/collapse ported from
panelUtils.ts as a React hook; Measure UI intentionally left
unwired per original app parity.

Typecheck and dev-server module serving verified; in-browser
rendering not yet verified in this session (no browser tool
available) — needs manual check.

Refs #1

src/components/DraggablePanel.tsx

@@ -0,0 +1,86 @@
+import type { ReactNode } from 'react';
+import { Card, CardContent, CardHeader, CardTitle, CardAction } from '@hm-design/ui';
+import { Button } from '@hm-design/ui';
+import { ChevronDown, ChevronRight, X } from 'lucide-react';
+import { useDraggablePanel } from '../hooks/useDraggablePanel';
+
+export interface DraggablePanelProps {
+  title: string;
+  icon?: ReactNode;
+  initial: { left: number; top: number };
+  width?: number;
+  height?: number;
+  open: boolean;
+  onClose: () => void;
+  headerActions?: ReactNode;
+  children: ReactNode;
+}
+
+export function DraggablePanel({
+  title,
+  icon,
+  initial,
+  width = 320,
+  height = 420,
+  open,
+  onClose,
+  headerActions,
+  children,
+}: DraggablePanelProps) {
+  const { panelRef, style, collapsed, toggleCollapse, headerProps } = useDraggablePanel(initial);
+
+  if (!open) return null;
+
+  return (
+    <Card
+      ref={panelRef}
+      size="sm"
+      className="fixed shadow-lg overflow-hidden"
+      style={{
+        ...style,
+        width,
+        height: collapsed ? 'auto' : height,
+        minWidth: 250,
+        minHeight: collapsed ? 'auto' : 140,
+        maxWidth: '90vw',
+        maxHeight: '90vh',
+        resize: collapsed ? 'none' : 'both',
+      }}
+    >
+      <CardHeader className="select-none border-b py-2" {...headerProps}>
+        <CardTitle className="flex items-center gap-2 text-sm">
+          {icon}
+          {title}
+        </CardTitle>
+        <CardAction className="flex items-center gap-1">
+          {headerActions}
+          <Button
+            type="button"
+            variant="ghost"
+            size="icon-xs"
+            aria-label={collapsed ? '펼치기' : '접기'}
+            title={collapsed ? '펼치기' : '접기'}
+            onClick={toggleCollapse}
+          >
+            {collapsed ? <ChevronRight /> : <ChevronDown />}
+          </Button>
+          <Button
+            type="button"
+            variant="ghost"
+            size="icon-xs"
+            aria-label="닫기"
+            title="닫기"
+            onClick={onClose}
+          >
+            <X />
+          </Button>
+        </CardAction>
+      </CardHeader>
+      {!collapsed && (
+        <CardContent className="overflow-auto" style={{ height: 'calc(100% - 44px)' }}>
+          {children}
+        </CardContent>
+      )}
+    </Card>
+  );
+}