Serve sculpt studio at /sculpt

Keep existing viewer URLs compatible and test embedded pages, assets, and isolation headers.

Amp-Thread-ID: https://ampcode.com/threads/T-01a0b4b4-202c-73f1-984d-9a55c88f9c83
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

server/app_test.go

@@ -217,6 +217,46 @@ func TestSavedPlaygroundPageRoute(t *testing.T) {
 	}
 }
 
+func TestSculptRoutesAndAssets(t *testing.T) {
+	routes := testApplication(t).routes()
+	for _, path := range []string{"/sculpt", "/sculpt/", "/view/sculpt", "/view/sculpt/", "/assets/sculpt/app.js", "/assets/sculpt/styles.css"} {
+		t.Run(path, func(t *testing.T) {
+			response := httptest.NewRecorder()
+			routes.ServeHTTP(response, httptest.NewRequest(http.MethodGet, path, nil))
+			if response.Code != http.StatusOK {
+				t.Fatalf("status = %d", response.Code)
+			}
+			for name, expected := range map[string]string{
+				"Cross-Origin-Opener-Policy":   "same-origin",
+				"Cross-Origin-Embedder-Policy": "require-corp",
+			} {
+				if got := response.Header().Get(name); got != expected {
+					t.Fatalf("%s = %q, want %q", name, got, expected)
+				}
+			}
+			switch path {
+			case "/assets/sculpt/app.js", "/assets/sculpt/styles.css":
+				expected := "text/javascript; charset=utf-8"
+				if filepath.Ext(path) == ".css" {
+					expected = "text/css; charset=utf-8"
+				}
+				if response.Header().Get("Content-Type") != expected || response.Body.Len() == 0 {
+					t.Fatalf("missing asset or wrong content type: %q", response.Header().Get("Content-Type"))
+				}
+			default:
+				if got := response.Header().Get("Content-Type"); got != "text/html; charset=utf-8" {
+					t.Fatalf("content type = %q", got)
+				}
+				for _, content := range []string{"<title>Sculpt — Yawn</title>", `src="/assets/sculpt/app.js"`, `href="/assets/sculpt/styles.css"`, `"@yawn/core": "/pkg/core.js"`} {
+					if !bytes.Contains(response.Body.Bytes(), []byte(content)) {
+						t.Fatalf("sculpt page missing %q", content)
+					}
+				}
+			}
+		})
+	}
+}
+
 func TestGltfViewerPageRoute(t *testing.T) {
 	request := httptest.NewRequest(http.MethodGet, "/view/gltf", nil)
 	response := httptest.NewRecorder()