feat(studio): enable timeline virtualization by default (#2926)

* feat(studio): enable timeline virtualization by default

* fix(ci): measure timeline performance in production React

packages/studio/src/hooks/studioTestMode.ts

@@ -0,0 +1,23 @@
+export type StudioRuntimeMode = "development" | "production";
+
+function readStudioImportMetaEnv(): ImportMetaEnv | undefined {
+  try {
+    return import.meta.env;
+  } catch {
+    return undefined;
+  }
+}
+
+const studioImportMetaEnv = readStudioImportMetaEnv();
+
+/**
+ * Test hooks belong to Vite's development server, even when that server uses
+ * production React for performance measurement. A production build has neither
+ * DEV nor the development server mode, so the API stays out of shipped assets.
+ */
+export const STUDIO_RUNTIME_MODE: StudioRuntimeMode = studioImportMetaEnv?.DEV
+  ? "development"
+  : "production";
+
+export const STUDIO_TEST_HOOKS_ENABLED =
+  studioImportMetaEnv?.DEV === true || studioImportMetaEnv?.MODE === "development";