docs(core-events): clarify subscribe consumerFeature + failFast drop

Code-quality review nits: IEventBus.subscribe docstring said "debug
tag" but InMemoryEventBus actually ignores the param entirely. Also
add a comment to InMemoryEventBus.publish noting that under failFast
only the first rejection rethrows; other failures are intentionally
dropped.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/core-events/src/event-bus.interface.ts

@@ -11,8 +11,8 @@ export interface IEventBus {
 
   /**
    * Subscribe a handler. `consumerFeature` is the kebab-case name of the
-   * subscribing feature (e.g., "marketing-pages"). InMemoryEventBus uses it
-   * only as a debug tag; PayloadJobsEventBus uses it to name the fan-out task
+   * subscribing feature (e.g., "marketing-pages"). It is unused by
+   * InMemoryEventBus; PayloadJobsEventBus uses it to name the fan-out task
    * slug deterministically (`__events.<event>.<consumerFeature>`).
    */
   subscribe<T>(

packages/core-events/src/in-memory-event-bus.ts

@@ -24,6 +24,8 @@ export class InMemoryEventBus implements IEventBus {
     );
     if (this.options.failFast) {
       const failure = settled.find((s) => s.status === "rejected");
+      // Only the first rejection is rethrown. Other failures are intentionally
+      // dropped — `failFast` is a test-affordance, not a fault-tolerance design.
       if (failure && failure.status === "rejected") throw failure.reason;
     }
   }