docs(ui): note the PWA limitation of the data-keyed context-menu gate

EPG previews are populated only where supportsEpg (Electron), so the
programme-details menu item cannot appear in the PWA today; the
data-presence gate is future-proofing, not PWA support (Codex review).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

libs/portal/stalker/feature/src/lib/stalker-live-stream-layout/stalker-live-stream-layout.component.ts

@@ -873,7 +873,12 @@ export class StalkerLiveStreamLayoutComponent implements OnDestroy {
         );
     }
 
-    /** Whether right-click has anything to offer for this row. */
+    /**
+     * Whether right-click has anything to offer for this row. Keys on data
+     * presence rather than runtime capability — but note EPG previews are
+     * currently populated only where `supportsEpg` (Electron), so in the PWA
+     * this stays false until portal EPG previews exist there.
+     */
     hasChannelContextMenu(item: StalkerItvChannel): boolean {
         return (
             this.supportsEpgMapping ||

libs/portal/xtream/feature/src/lib/portal-channels-list/portal-channels-list.component.ts

@@ -512,7 +512,12 @@ export class PortalChannelsListComponent implements AfterViewInit, OnDestroy {
         return this.epgPrograms.get(channel.xtream_id) ?? null;
     }
 
-    /** Whether right-click has anything to offer for this row. */
+    /**
+     * Whether right-click has anything to offer for this row. Keys on data
+     * presence rather than runtime capability — but note EPG previews are
+     * currently populated only where `supportsEpg` (Electron), so in the PWA
+     * this stays false until portal EPG previews exist there.
+     */
     hasChannelContextMenu(item: XtreamChannelListItem): boolean {
         return this.supportsEpgMapping || this.epgPrograms.has(item.xtream_id);
     }