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]>

src/ingest/adapters/index.ts

@@ -123,6 +123,16 @@ const SOURCES: SourceSpec[] = [
     url: "https://holodori.wiki/wiki/Events",
     parserId: "holodoriwiki",
   },
+  {
+    id: "gfl2-iopwiki-events",
+    game: "gfl2",
+    // IOP Wiki, the Girls' Frontline universe wiki. Its robots.txt is two lines
+    // — `User-agent: *` and `Crawl-Delay: 20` — with no Disallow anywhere, and
+    // the page answers our own User-Agent with a 200 and a real `Last-Modified`,
+    // so the conditional request below costs it a 304 on an unchanged day.
+    url: "https://iopwiki.com/wiki/GFL2_Events",
+    parserId: "iopwiki",
+  },
 ];
 
 function toAdapter(spec: SourceSpec): Adapter {