feat: add Girls' Frontline 2, from IOP Wiki

The best date material this project has after wiki.gg: every row states an
exact instant on both boundaries and names the zone, so nothing is converted
and nothing is assumed. `parseIsoClockRangeUtc` requires that `(UTC)` rather
than defaulting to it — a row that ever loses it should drop out instead of
landing hours off a boundary the reader is watching in-game.

The hazard here is the Server column. CN, EN and JP rows share one table and
the Chinese schedule runs about a year ahead, which is the akwiki CN-column
problem verbatim: publish EN, skip the rest. Betas are fenced off separately,
being dated exactly like everything else and playable by nobody, and the page
is an archive back to 2023, so currency is decided against ctx.now as in
bawiki. That leaves one live event today — thin, and true.

No resetOffsets: the EN boundaries land on three different clocks, which is a
patch window rather than a reset hour.

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

docs/DATA-MODEL.md

@@ -10,7 +10,7 @@ import { z } from "zod";
 
 export const GameId = z.enum([
   "genshin", "hsr", "zzz", "wuwa", "arknights", "endfield", "nte", "nikki", "p5x", "r1999",
-  "ba", "fgo", "holodori",
+  "ba", "fgo", "holodori", "gfl2",
 ]);
 
 export const EventType = z.enum([
@@ -308,8 +308,16 @@ nothing to add, which is the point worth carrying to the next game: an override
 the game moves nobody, while the same override added a year later re-labels every tick already
 logged under the old clock. Get it right at introduction or accept a migration.
 
-Infinity Nikki, P5X and Blue Archive carry **no `resetOffsets` entry**, so they take the regional
-default. That is an assumption, not a verified server map — none of the three sources states one.
+Infinity Nikki, P5X and Blue Archive carry **no `resetOffsets`
+entry**, so they take the regional default. That is an assumption, not a verified server map — none
+of those sources states one. The 2026-08-19 addition below is worth separating out, because it is
+silent for a different reason than the usual one:
+
+- **Girls' Frontline 2** states an exact UTC instant on every boundary, so the data is there and
+  still settles nothing: its EN events end at 22:59 (33 of them), 08:59 (11) and 02:59 (5). Arknights
+  and Reverse: 1999 each earned an override from a single boundary the whole page agreed on; three
+  of them is a patch window, not a reset hour.
+
 Blue Archive is the case where the assumption is most likely wrong and still the right entry: the
 game does run one worldwide server, but `bluearchive.wiki` states no time of day and no timezone
 anywhere on the page, so there is no offset to read off it. Confirm these against the games before