docs(xtream): note why the seasons service is injected last

Its TMDB enrichment effect keeps the position it had as the first effect
of the component constructor only while it is created after the other
services' effects.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

libs/portal/xtream/feature/src/lib/serial-details/serial-details.component.ts

@@ -166,7 +166,11 @@ export class SerialDetailsComponent implements OnDestroy {
     readonly similarItems = this.similar.similarItems;
     readonly similarInPortals = this.similar.similarInPortals;
 
-    /** Season descriptions and posters, and the selected season's enrichment. */
+    /**
+     * Season descriptions and posters, and the selected season's enrichment.
+     * Injected after the other services that register effects: its enrichment
+     * effect then runs after theirs and before the constructor's.
+     */
     private readonly seasons = inject(SerialDetailsSeasonsService);
     readonly seasonDescriptions = this.seasons.descriptions;
     readonly seasonPosters = this.seasons.posters;