fix(portals): probe like playback, and stop the pin answering for a remake

Five findings from the latest review pass.

Writing a pin to every alias — last round's fix for stale aliases — was
wrong in the other direction: `title:{base}:` is shared by every remake, so
a known-year decision stored there answers for a different film. Pin Dune
(2021), open Dune (1984) before its year arrives, and it would start the
2021 source. A write now clears every alias and stores only the canonical
key, which retires the stale ones without making any of them ambiguous.

The probe checked a bare URL while playback sends the playlist's User-Agent,
Referer and Origin. A panel that requires them answers 401/403, so a stream
that plays perfectly was reported dead and penalised in failover ranking.

The switch toast interpolated the raw playlist name. Users routinely name a
playlist after the URL they pasted, so that line could put credentials over
the video; the notice now carries the same safe label the rows use.

External players have no timeupdate, so their polled position IS the live
one. Feeding it through the seed — which stops at the first value — froze
the resume point where playback started, and a switch an hour in rewound to
the beginning.

And auto-failover concluded "nowhere to go" when a stream failed before
discovery answered, stranding the user on the error screen.

Moves `switchTo` into the session module, which is where the rest of the
switch mechanics already live, and splits the route spec along the same
rendering/behaviour seam the other suites use.

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

libs/shared/interfaces/src/lib/electron-api.interface.ts

@@ -33,6 +33,7 @@ import {
 import { PortalDebugEvent } from './portal-debug.interface';
 import { CatalogTitleMatch } from './catalog-title-match.interface';
 import {
+    StreamProbeHeaders,
     VodSourceCandidateRow,
     VodSourcePin,
 } from './vod-source.interface';
@@ -688,7 +689,9 @@ export interface ElectronBridgeApi {
     /** Generic stream reachability probe (VOD multi-source availability) */
     probeStreamUrl: (
         url: string,
-        method?: 'GET' | 'HEAD'
+        method?: 'GET' | 'HEAD',
+        /** Playback headers the owning playlist requires, when it has any. */
+        headers?: StreamProbeHeaders
     ) => Promise<ElectronBridgeXtreamProbeResult>;
     refreshPlaylist: (
         payload: PlaylistRefreshPayload

libs/shared/interfaces/src/lib/vod-source.interface.ts

@@ -51,6 +51,19 @@ export type VodSourceProbeStatus =
      */
     | 'unknown';
 
+/**
+ * Playback headers a playlist requires, carried into the probe.
+ *
+ * A panel configured to demand its own User-Agent, Referer or Origin answers
+ * 401/403 without them, and calling a stream that plays fine "unavailable" is
+ * exactly the confident lie this feature refuses to tell.
+ */
+export interface StreamProbeHeaders {
+    userAgent?: string | null;
+    referer?: string | null;
+    origin?: string | null;
+}
+
 export interface VodSourceProbeResult {
     status: VodSourceProbeStatus;
     /** HTTP status when one was actually received; 0 when none was. */