chore(dev): add React profiling and focused A/B workflows

scripts/react/delay.ts

@@ -0,0 +1,36 @@
+type Update = { delay: number; elapsed?: number; updatedAt: number }
+const listeners = new Map<string, (update: Update) => void>()
+const cache = new Map<string, Update>()
+let finish: ((update: Update) => void) | undefined
+const key = (name: string, group: string) => `${group}:${name}`
+export const delayFixture = {
+  listeners,
+  emit(name: string, group: string, update: Update) {
+    cache.set(key(name, group), update)
+    listeners.get(key(name, group))?.(update)
+  },
+  finish(update: Update) {
+    if (!finish) throw new Error('No pending delay request')
+    finish(update)
+    finish = undefined
+  },
+}
+export default {
+  setListener(name: string, group: string, listener: (update: Update) => void) {
+    listeners.set(key(name, group), listener)
+  },
+  removeListener(name: string, group: string) {
+    listeners.delete(key(name, group))
+  },
+  getDelayUpdate(name: string, group: string) {
+    return cache.get(key(name, group))
+  },
+  getDelayFix() {
+    return -1
+  },
+  checkDelay() {
+    return new Promise<Update>((resolve) => {
+      finish = resolve
+    })
+  },
+}