feat: add Umamusume, from Game8's banner list

uma.moe stays declined — its API sits behind a Cloudflare Turnstile proof
header, and an adapter would mean defeating a deliberate access control. This
is the surface that is simply open, and it needed the parser change in the
commit before this one to be readable at all.

The stable URL matters: Game8 also publishes monthly "August 2026 Release
Schedule" pages whose id changes every month, which a static registry cannot
follow. "List of All Banners" does not move.

Four current banners, both columns of the side-by-side table, and none of the
Previous Banners below them. The tenth game8 source, so it carries the same CI
blindness as the other nine and only a manual refresh moves it.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

docs/PRD.md

@@ -59,7 +59,7 @@ have a source — this table is the launch scope, not a roster to keep in sync.
 
 Adding a game must require no change to `GachaEvent` — only a `GameId` entry, its `games.ts`
 metadata, and a source registration. That is the test of whether the data model is right, and it has
-held: the sixteen games here have cost the event schema nothing. Per-game *metadata* does occasionally
+held: the seventeen games here have cost the event schema nothing. Per-game *metadata* does occasionally
 grow (Reverse: 1999 needed `resetHourLocal` for a 05:00 reset), which is a different file and moves
 no stored key. A game may have several sources; see `docs/INGESTION.md` § Three layers.
 
@@ -90,7 +90,7 @@ default `"game"` — the board every existing reader already has). Merged, the o
 `endingSoonestFirst`, the same comparator behind the list's "Ending soonest" (F2), so the two views
 cannot mean different things by the same words and an unannounced end still sorts behind every dated
 one rather than claiming a place in the queue. Merged there is also no lane heading to say whose
-event a bar is, and hue alone cannot answer that once sixteen games share a stack — so each bar
+event a bar is, and hue alone cannot answer that once seventeen games share a stack — so each bar
 carries its game's short name, with the full name in its tooltip. A bar too narrow for a tag and a
 title both keeps the title: a chopped game name reads as a broken word, and the hue and the tooltip
 still answer it.