feat(core): reload agents from config change feed (#39167)

packages/core/test/lib/clock.ts

@@ -0,0 +1,38 @@
+import { Effect } from "effect"
+import { TestClock } from "effect/testing"
+
+// Defers on a real macrotask so pubsub delivery, fiber hops, and filesystem
+// work can complete between TestClock advances.
+const settle = Effect.promise(() => new Promise((resolve) => setTimeout(resolve, 1)))
+
+// One advance step: let pending real work finish, then fire due TestClock timers.
+const tick = Effect.gen(function* () {
+  yield* settle
+  yield* TestClock.adjust("500 millis")
+})
+
+/**
+ * Drives every pending TestClock timer to completion: stream debounces and
+ * State's 500ms reload debounce register their sleeps from separate fiber hops
+ * that a single adjust can miss, so the loop alternates real-macrotask settles
+ * with adjusts until the condition holds. Extra adjusts are harmless when
+ * nothing is pending.
+ */
+export const advance = Effect.fnUntraced(function* (condition: () => boolean) {
+  for (let attempt = 0; attempt < 100; attempt++) {
+    if (condition()) return
+    yield* tick
+  }
+  return yield* Effect.die(new Error("condition never became true after 100 advances"))
+})
+
+/**
+ * Advances far enough that any pending debounced work would have completed,
+ * so a no-op assertion afterwards is meaningful.
+ */
+export const drain = Effect.gen(function* () {
+  for (let round = 0; round < 4; round++) {
+    yield* tick
+  }
+  yield* settle
+})