Initial public release: DWG/DXF 2D viewer sample

Standalone Vite sample composing acadrust-dwg WASM, dxf-parser, and Viewer2D.

src/viewer2d/ext2d.ts

@@ -0,0 +1,25 @@
+/**
+ * 2D file-format detection for the 2D+3D merge dispatch.
+ *
+ * 2D = CAD drawings (dwg/dxf) → rendered by Viewer2D via the WASM parser.
+ * Everything else (glb/gltf/obj/fbx/dae/ifc/ply/3ds/3dm) is 3D → ThreeDViewer.
+ * Kept dependency-free so both the dropzone and the controller can import it
+ * without pulling in either viewer.
+ */
+export const DWG_EXT = /\.dwg$/i;
+export const DXF_EXT = /\.dxf$/i;
+
+/** True if the name is a binary DWG (parsed by the WASM parser). */
+export function isDwg(name: string): boolean {
+  return DWG_EXT.test(name);
+}
+
+/** True if the name is a text DXF (parsed by the dxf-parser JS lib). */
+export function isDxf(name: string): boolean {
+  return DXF_EXT.test(name);
+}
+
+/** True if the file/URL name is a 2D CAD drawing (dwg or dxf) → Viewer2D. */
+export function is2D(name: string): boolean {
+  return DWG_EXT.test(name) || DXF_EXT.test(name);
+}