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>

docs/architecture/playlist-backup-restore.md

@@ -162,7 +162,12 @@ worker IPC boundary in the snake_case wire shape declared by
 `XCategoryFromDb`/`XtreamCategoryFromDb`; the category operations project
 their Drizzle rows explicitly to keep that contract true.
 
-`sourcePins` (VOD multi-source) is the one **optional** collection: archives
+`sourcePins` (VOD multi-source) is the one **optional** collection, and the
+normalizer preserves that: an absent field stays absent rather than becoming
+`[]`, because restore treats a PRESENT collection as authoritative and clears
+the playlist's existing pins before applying it. Materializing an empty array
+would turn "this archive predates pins" into "this archive says there are
+none": archives
 written before multi-source existed simply do not have it, so its absence is
 age rather than damage and only a wrong type is rejected. A pin is carried
 under the playlist it points AT — exporting it anywhere else would restore a