feat(core-events): PayloadJobsEventBus (fan-out via IJobQueue)

TDD: red (test-only), then green. PayloadJobsEventBus validates before
enqueueing, names tasks __events.<event>.<consumer> deterministically, and
enqueues one task per subscriber via Promise.all. 3 new tests (11 total).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-events/src/payload-jobs-event-bus.ts

@@ -0,0 +1,43 @@
+import type { z } from "zod";
+import type { IJobQueue } from "@repo/core-shared/jobs";
+import type { EventDescriptor } from "./event-descriptor";
+import type { EventHandler, IEventBus } from "./event-bus.interface";
+
+/**
+ * Production-grade bus: for each subscriber, enqueues one Payload task per
+ * `publish()` call. Subscribers register with their consumer-feature name so
+ * fan-out tasks are named deterministically: `__events.<event>.<consumer>`.
+ * The actual handler invocation happens inside Payload's job runner — see the
+ * matching task config generated by `gen event consume` (Task 39).
+ */
+export class PayloadJobsEventBus implements IEventBus {
+  private readonly subscribers = new Map<string, string[]>();
+
+  constructor(private readonly queue: IJobQueue) {}
+
+  async publish<T>(
+    descriptor: EventDescriptor<string, z.ZodType<T>>,
+    payload: T,
+  ): Promise<void> {
+    descriptor.schema.parse(payload);
+    const consumers = this.subscribers.get(descriptor.name) ?? [];
+    await Promise.all(
+      consumers.map((consumerFeature) =>
+        this.queue.enqueue(
+          `__events.${descriptor.name}.${consumerFeature}`,
+          payload,
+        ),
+      ),
+    );
+  }
+
+  subscribe<T>(
+    descriptor: EventDescriptor<string, z.ZodType<T>>,
+    consumerFeature: string,
+    _handler: EventHandler<T>,
+  ): void {
+    const arr = this.subscribers.get(descriptor.name) ?? [];
+    if (!arr.includes(consumerFeature)) arr.push(consumerFeature);
+    this.subscribers.set(descriptor.name, arr);
+  }
+}