fix(ingest): support redesigned Blue Archive wiki event table

The Blue Archive Wiki (bluearchive.wiki/wiki/Events) redesigned its
schedule, replacing the per-version MediaWiki tabber with a unified
#eventtable displaying JP and Global periods side-by-side.

- Parse #eventtable resolving GL Period, event titles, and article links
  from .event-region-gl, with fallback to .event-region-jp.
- Maintain backwards compatibility with legacy tabber schedule format.
- Add pinned fixture fixtures/ba/bawiki-events-2026-09-17 and tests.
- Update snapshot, AGENTS.md, ARCHITECTURE.md, and INGESTION.md.

docs/ARCHITECTURE.md

@@ -76,7 +76,7 @@ src/
       wikigg.ts         wiki.gg mp-event templates                ✓ built
       akwiki.ts         arknights.wiki.gg mrfz-wtable             ✓ built
       fandom.ts         Fandom via the action=parse API           ✓ built
-      bawiki.ts         bluearchive.wiki JP/Global tabber         ✓ built
+      bawiki.ts         bluearchive.wiki schedule (#eventtable & tabber) ✓ built
       holodori.ts       holodori.wiki Current/Past Events tables   ✓ built
       index.ts          parser registry                           ✓ built
     adapters/