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

package.json

@@ -0,0 +1,34 @@
+{
+  "name": "dwg-dxf-viewer-hm",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "workspaces": [
+    "HMDesign/packages/ui"
+  ],
+  "scripts": {
+    "dev": "vite --port 5173 --strictPort",
+    "build": "tsc -b --noEmit && vite build",
+    "preview": "vite preview",
+    "typecheck": "tsc -b --noEmit"
+  },
+  "dependencies": {
+    "@hm-design/ui": "*",
+    "dxf-parser": "^1.1.2",
+    "lucide-react": "^1.49.0",
+    "opentype.js": "^2.0.0",
+    "react": "19.3.0",
+    "react-dom": "19.3.0",
+    "three": "^0.185.1"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "4.3.3",
+    "@types/react": "19.3.0",
+    "@types/react-dom": "19.3.0",
+    "@types/three": "^0.185.1",
+    "@vitejs/plugin-react": "^4.3.0",
+    "tailwindcss": "4.3.3",
+    "typescript": "^5.6.0",
+    "vite": "^5.4.0"
+  }
+}