feat: a bare URL opens on FiDi, not on 1,551 km of tan

One California is the product; the first frame is still the coarsest
pose the pack owns, because createScene opens on chapters[0] and the
state tour starts there. Capture and ?city=california keep that.
A visitor typing tera.lumbridgecorp.com gets openingChapter fidi —
a city they can read — without reordering the pack.

src/main.ts

@@ -339,9 +339,10 @@ const CITIES: { id: string; label: string; city: City }[] = ONE_CALIFORNIA
 /*
  * With one board there is nothing to choose: the argument above is entirely
  * about which of three products a bare URL lands on, and `?one=1` is the answer
- * that there are not three. The landing *pose* is a separate question and still
- * belongs to the chapter list — `california-overview` frames the state, and the
- * metro rungs restored in `cities/unify.ts` are how you get down from it.
+ * that there are not three. The landing *pose* is a separate question: the
+ * pack still opens its chapter list on `california-overview` so capture and
+ * `?city=california` frame the state, and a bare URL passes `openingChapter:
+ * "fidi"` so a visitor's first frame is a city they can read.
  */
 const DEFAULT_CITY_ID = ONE_CALIFORNIA ? "california" : "sf";
 
@@ -1916,6 +1917,9 @@ async function buildBoard(
   const drawsMigration = carriesSky && access.feeds?.birds === true;
   const handle = await createScene(stage, {
     city: entry.city,
+    // Bare URL on one California: land in the city, not on 1,551 km of state.
+    // `?city=california` (and every capture shot) still opens on chapters[0].
+    ...(ONE_CALIFORNIA && CITY_PARAM === null ? { openingChapter: "fidi" } : {}),
     // The page's one rig, shared with the office. Handed in rather than built
     // per board; see the note where it is constructed.
     environment,