fix(portals): gate VOD auto-failover on engines that can report failures

Merges master and resolves the collision with its shared playback helpers,
then closes two Codex findings.

Master extracted the Play/Stop button state and the inline position writer
that this branch had modified. Rather than forking private copies back out of
Xtream, both behaviours move into the shared helpers: `alsoOwns` lets a page
own an external session launched for a copy of the same film in another
playlist, and the resume latch — which stops a timeupdate emitted before the
engine reaches `startTime` from overwriting the point being resumed from —
now protects Stalker too, which had the same bug.

Auto-failover was offered on every engine, but only the built-in web players
raise the playback diagnostic that reaches `onPlaybackFailed()`: Embedded MPV
has its diagnostics suppressed and MPV/VLC play outside the app. The toggle is
now hidden there, in settings and in the sources menu, instead of promising a
switch that can never happen.

`setAutoFailover` also ignored `updateSettings()`, which patches memory first
and rejects if the write fails — the toggle looked saved, silently reverted on
restart, and the rejection surfaced only as an unhandled promise. It now
reports the failure like the settings form's own save paths.

The three VOD-details route specs each carried a near-identical 150-line
TestBed; they now share one harness, which is what makes room for the new
cases (1012 -> 584 lines).

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

libs/ui/components/src/lib/vod-sources/vod-sources-chip.component.html

@@ -39,6 +39,7 @@
         [title]="title()"
         [matchKind]="matchKind()"
         [autoFailoverEnabled]="autoFailoverEnabled()"
+        [autoFailoverSupported]="autoFailoverSupported()"
         [resumeLabel]="resumeLabel()"
         [showPin]="showPin()"
         (playRequested)="onPlay($event)"

libs/ui/components/src/lib/vod-sources/vod-sources-chip.component.ts

@@ -42,6 +42,8 @@ export class VodSourcesChipComponent {
     readonly title = input('');
     readonly matchKind = input<VodSourceMatchKind>('title-year');
     readonly autoFailoverEnabled = input(false);
+    /** See `VodSourcesMenuComponent.autoFailoverSupported`. */
+    readonly autoFailoverSupported = input(true);
     readonly resumeLabel = input<string | null>(null);
     readonly showPin = input(true);
     /** Falls back to the number of sources when the host does not override it. */

libs/ui/components/src/lib/vod-sources/vod-sources-menu.component.html

@@ -120,16 +120,20 @@
         }
     </div>
 
-    <div class="sources-menu__footer">
-        <span class="sources-menu__footer-label">{{
-            'PORTALS.MULTI_SOURCE.AUTO_FAILOVER' | translate
-        }}</span>
-        <mat-slide-toggle
-            class="sources-menu__toggle"
-            [checked]="autoFailoverEnabled()"
-            (change)="onAutoFailoverChange($event)"
-            (click)="$event.stopPropagation()"
-            [attr.aria-label]="'PORTALS.MULTI_SOURCE.AUTO_FAILOVER' | translate"
-        />
-    </div>
+    @if (autoFailoverSupported()) {
+        <div class="sources-menu__footer">
+            <span class="sources-menu__footer-label">{{
+                'PORTALS.MULTI_SOURCE.AUTO_FAILOVER' | translate
+            }}</span>
+            <mat-slide-toggle
+                class="sources-menu__toggle"
+                [checked]="autoFailoverEnabled()"
+                (change)="onAutoFailoverChange($event)"
+                (click)="$event.stopPropagation()"
+                [attr.aria-label]="
+                    'PORTALS.MULTI_SOURCE.AUTO_FAILOVER' | translate
+                "
+            />
+        </div>
+    }
 </div>

libs/ui/components/src/lib/vod-sources/vod-sources-menu.component.spec.ts

@@ -243,6 +243,22 @@ describe('VodSourcesMenuComponent', () => {
         expect(emitted).toEqual([true]);
     });
 
+    it('drops the footer switch on a player that cannot report failures', () => {
+        // MPV, VLC and Embedded MPV never raise the playback diagnostic that
+        // drives failover, so the switch there promises something that can
+        // never happen.
+        render([createSource()]);
+        fixture.componentRef.setInput('autoFailoverSupported', false);
+        fixture.detectChanges();
+
+        expect(
+            fixture.debugElement.query(By.css('.sources-menu__toggle'))
+        ).toBeNull();
+        expect(fixture.nativeElement.textContent).not.toContain(
+            'Auto-switch on error'
+        );
+    });
+
     it('shows the match kind in the header, or the resume label when given', () => {
         fixture.componentRef.setInput('sources', [createSource()]);
         fixture.componentRef.setInput('matchKind', 'tmdb');

libs/ui/components/src/lib/vod-sources/vod-sources-menu.component.ts

@@ -56,6 +56,12 @@ export class VodSourcesMenuComponent {
     readonly title = input('');
     readonly matchKind = input<VodSourceMatchKind>('title-year');
     readonly autoFailoverEnabled = input(false);
+    /**
+     * False on players that never report a playback failure (MPV, VLC,
+     * Embedded MPV). The toggle would then promise a switch that can never
+     * happen, so it is not offered at all.
+     */
+    readonly autoFailoverSupported = input(true);
     /**
      * In-player variant: replaces the match kind with e.g.
      * "timecode will be kept · 0:42:18". Already formatted by the host.