feat(prefs): ask which view to open on, and remember the answer

`view` was component state, so a reader who preferred the timeline was put
back on the list by every reload — and which view opened at all had been
decided for them twice over: the PRD said calendar, the app shipped the list.
Neither was the reader's answer.

So the first run asks, and the tabs write to `prefs` from then on. The
question ships pre-answered with the list, because a reader cannot choose
between two layouts they have not seen and that is the one that answers "what
expires next" in a look — and each option is drawn rather than described, for
the same reason. The screen says where to change it afterwards, since the tabs
are small text in a corner.

Adds `view` to the prefs key space. Additive and defaulted, so an existing
reader's stored prefs open exactly where they did before.

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

docs/ARCHITECTURE.md

@@ -108,7 +108,7 @@ src/
       Fireworks.tsx     the burst when the last daily lands
       GameFocus.tsx     one game at a time          (F4a)
       Controls.tsx      games, region, export/import(F4, F5, F6)
-      Welcome.tsx       first-run game picker       (F8)
+      Welcome.tsx       first-run games and view    (F8)
       Toast.tsx         undo an ignore
       UpdateNotice      a newer app is installed and waiting  (F14)
       YourOwn.tsx       the reader's own games, in settings   (F13)
@@ -119,7 +119,7 @@ src/
       useMarkSet.ts     ignores (and the superseded completions shape)
       useProgress.ts    status, effort, note, daily override  (F12)
       useDailyLog.ts    which game-days are ticked off
-      usePrefs.ts       region, filters, focus, onboarding flags
+      usePrefs.ts       region, filters, focus, view, onboarding flags
       useCustom.ts      the reader's own games and events     (F13)
       gameMeta.tsx      lane id → name, label, hue; resolves custom lanes too
       sort.ts           deadline order, or what you're partway through