doc: Add clarifying comment for hub on ACS (#11633)

Added a comment for
#11630 (comment)!

Author: mydea

packages/core/src/asyncContext/stackStrategy.ts

@@ -132,9 +132,13 @@ export class AsyncContextStack {
  */
 function getAsyncContextStack(): AsyncContextStack {
   const registry = getMainCarrier();
+
+  // For now we continue to keep this as `hub` on the ACS,
+  // as e.g. the Loader Script relies on this.
+  // Eventually we may change this if/when we update the loader to not require this field anymore
+  // Related, we also write to `hub` in {@link ./../sdk.ts registerClientOnGlobalHub}
   const sentry = getSentryCarrier(registry) as { hub?: AsyncContextStack };
 
-  // If there's no hub, or its an old API, assign a new one
   if (sentry.hub) {
     return sentry.hub;
   }

packages/core/src/sdk.ts

@@ -48,11 +48,11 @@ export function setCurrentClient(client: Client): void {
 }
 
 /**
- * Unfortunately, we still have to manually bind the client to the "hub" set on the global
+ * Unfortunately, we still have to manually bind the client to the "hub" property set on the global
  * Sentry carrier object. This is because certain scripts (e.g. our loader script) obtain
  * the client via `window.__SENTRY__.hub.getClient()`.
  *
- * @see {@link hub.ts getGlobalHub}
+ * @see {@link ./asyncContext/stackStrategy.ts getAsyncContextStack}
  */
 function registerClientOnGlobalHub(client: Client): void {
   const sentryGlobal = getSentryCarrier(getMainCarrier()) as { hub?: AsyncContextStack };