perf: reduce 3D runtime artifacts (#7)

tests/decoder-staging.test.ts

@@ -1,5 +1,5 @@
 import { createHash } from 'node:crypto';
-import { readFileSync, statSync } from 'node:fs';
+import { existsSync, readFileSync, statSync } from 'node:fs';
 import { dirname, resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { describe, expect, it } from 'vitest';
@@ -11,21 +11,25 @@ function sha256(path: string): string {
 }
 
 describe('decoder staging', () => {
-  it('copies decoder binaries byte-for-byte without executable permission', () => {
-    const threeRoot = resolve(
-      dirname(fileURLToPath(import.meta.resolve('three'))),
-      '..',
-    );
+  it('stages only the single-thread IFC runtime', () => {
+    expect(
+      existsSync(
+        resolve(projectRoot, 'apps/viewer-3d/public/web-ifc/web-ifc-mt.wasm'),
+      ),
+    ).toBe(false);
+  });
+
+  it('does not stage decoder copies already bundled by Three.js', () => {
+    for (const directory of ['draco', 'basis']) {
+      expect(
+        existsSync(resolve(projectRoot, 'apps/viewer-3d/public', directory)),
+      ).toBe(false);
+    }
+  });
+
+  it('copies the IFC binary byte-for-byte without executable permission', () => {
     const ifcRoot = dirname(fileURLToPath(import.meta.resolve('web-ifc')));
     const pairs = [
-      [
-        resolve(threeRoot, 'examples/jsm/libs/draco/gltf/draco_decoder.wasm'),
-        resolve(projectRoot, 'apps/viewer-3d/public/draco/draco_decoder.wasm'),
-      ],
-      [
-        resolve(threeRoot, 'examples/jsm/libs/basis/basis_transcoder.wasm'),
-        resolve(projectRoot, 'apps/viewer-3d/public/basis/basis_transcoder.wasm'),
-      ],
       [
         resolve(ifcRoot, 'web-ifc.wasm'),
         resolve(projectRoot, 'apps/viewer-3d/public/web-ifc/web-ifc.wasm'),