fix(portals): absent is not empty, and every start claims the generation

Four more from review, three of them defects in last round's fixes.

The restore normalizer materialized `sourcePins: []` for archives that never
had the field, so "absent means no opinion" became "this archive says there
are no pins" and a merge cleared the user's. Absent now stays absent. My test
for that behaviour had passed for the wrong reason — it stubbed an empty pin
list, so the clear was skipped whether or not the guard worked.

`startGeneration` was claimed only by the switch path, so a plain Play, Resume
or Restart could be overtaken by a switch still awaiting its close. Every
start claims it now.

Raw and normalized tokens were paired by position, which breaks when
normalization drops a whole word: "FR: Ça" normalizes to "ca" and got handed
the raw token "FR:", sending it down the ASCII branch it cannot match from.
They are paired by normalized form instead.

And the ambiguous yearless alias (`title:dune:`) is no longer written or
retired beside a precise key — it may hold another remake's pre-enrichment
pin. It stays available when it is the only key there is, since refusing to
pin at all would be worse.

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

libs/services/src/lib/playlist-backup.service.pins.spec.ts

@@ -25,7 +25,6 @@ describe('PlaylistBackupService Xtream source pins', () => {
         localStorage.clear();
     });
 
-
     it('exports the pins that point at this playlist', async () => {
         const collaborators = createRestoreCollaborators();
         const service = createPlaylistBackupService({
@@ -147,7 +146,16 @@ describe('PlaylistBackupService Xtream source pins', () => {
         const service = createPlaylistBackupService({
             ...collaborators,
             vodSourcePinService: {
-                listForPlaylist: jest.fn().mockResolvedValue([]),
+                // A pin EXISTS, or an empty list would make this pass whether
+                // or not the clear was skipped.
+                listForPlaylist: jest.fn().mockResolvedValue([
+                    {
+                        matchKey: 'tmdb:999',
+                        playlistId: 'xtream-1',
+                        contentId: 7,
+                        portalType: 'xtream',
+                    },
+                ]),
                 set: jest.fn().mockResolvedValue(true),
                 clear: clearPins,
             },