Write down that a source can be empty without being broken

The two preceding changes make sentences in docs/ false. INGESTION.md
described `canParse` as a structural check without saying that "structural"
excludes the presence of a row — which is exactly the drift that let this
bug in — and described the Stage 1 gate as rejecting every empty parse.
SOURCES.md § 11 left a reader to conclude that an empty Infinity Nikki lane
means the source has died.

AGENTS.md gets the rule in both places somebody would look: § Working on
parsers, next to the bullet about a source resting on one row, and § Fandom
where the fourth template is described.

The general lesson is worth more than the incident. Any page that can list
nothing can produce this, so the guidance is about what identifies a page
versus what happens to be on it — not about this wiki.

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

AGENTS.md

@@ -254,6 +254,12 @@ These come from how gacha games actually schedule things, and they cause most bu
   refresh reported a shape change. Neither number was ever a count of the page. When a source's
   count is far below what the page shows, find out which shape is being skipped before the count
   reaches zero and the gate has to guess for you.
+- **A count of zero has two causes, and only the page can tell them apart.** A source that broke and
+  a game that is between patches both read `0`, so nothing downstream can separate them — which is
+  why `canParse` must identify a page by its *structure* (headings, ids, column names) and never by
+  finding a row, and why a page that prints something like `There are no Events in this category`
+  gets to say so through `statesNoEvents` rather than being counted as a failure. Infinity Nikki hit
+  both halves of this at once; see § Fandom.
 
 ## Event IDs are localStorage keys
 
@@ -618,6 +624,29 @@ by hand**, because an attribute never passes through `text()` and `Alison's
 otherwise become a slug, and a slug is a localStorage key. The sanitiser catches exactly that, and a
 parser needing repair on its own fixture is a parser with a bug.
 
+**This page goes empty between versions, and that is a third thing a source can be.** On 2026-09-03,
+with 2.7's events ended and 2.8 not yet listed, the wiki replaced both tables with `There are no
+Events in this category` — the markup otherwise untouched, `Past Events` still carrying twenty
+tables of the same shape. `isInfinityNikkiEventPage` identified the page by finding a *populated*
+table, so it read that as a redesign, and the source spent four cycles reporting
+`the source has likely been redesigned` at a page nobody had redesigned. Two rules came out of it,
+and both generalise past this wiki:
+
+- **A `canParse` that reads data cannot tell a rewrite from a quiet week.** It now reads the section
+  headings, which an empty table does not take with it — *either* `Current Events` or
+  `Upcoming Events`, not both, because requiring the pair would fail the source over a renamed
+  heading it does not even read. `docs/INGESTION.md` already said to keep these checks structural;
+  this one had drifted into content and nothing caught it until a game went quiet.
+- **A page that states its own emptiness is answering, not failing.** `statesNoEvents` (optional on
+  `SourceParser`) lets the runner store that as a real answer, so the snapshot advances and the
+  streak stays clean instead of reaching the `broken` tier over a correctly empty lane. It must rest
+  on the page's own words — a redesign yields zero rows too, and storing *that* is the silent
+  emptying the zero-events gate exists to prevent. Only this template implements it; the other three
+  say nothing either way when empty and keep the strict gate.
+
+An empty Nikki lane is therefore now the truth rather than a gap, exactly as GFL2's thin weeks are.
+The lane refills on its own when 2.8 is listed, with no parser change.
+
 **The second Fandom source's page is chosen, not obvious.**
 `fategrandorder.fandom.com` publishes two schedules: `Event_List` opens "This page lists all Events
 in Fate/Grand Order Japan", and `Event_List_(US)` is the English server. They run months apart, each