The selected companion everywhere, each with a small trait; next-APK notes

- state/companion.ts: one store for the chosen companion (also in localStorage so splash/login show it).
  BrandMark (the orange «π» tile) now shows the companion's symbol (Σ Δ π ω) in its colour; screen-header
  mascots, loaders and empty/error states default to it; the assistant is «از {name} بپرس» with its face,
  colour and wording; the shop, lesson and quiz «ask» buttons name it; the active tab takes its tint.
- Traits, all client-side and light: Σ sigma keeps a running tally of correct answers in the quiz header;
  Δ delta shows a flame «×N» chip and an extra buzz for answers in a row; π pi gives a short solving tip
  after a wrong answer; ω omega throws gold confetti at the end of every island whatever the score.
  Each companion's «correct» sound is pitched differently; confetti uses its colours. Characters screen
  lists each trait.
- android/README.md: what MainActivity.kt has that the installed APK lacks (vibrate bridge, media gesture,
  in-app gateway + paysInApp), what to check on a phone after building, signing owner, Bazaar policy note.

Checked in headless Chrome with Sigma, Delta and Omega selected (home, assistant, shop, characters, quiz).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/screens/StreakScreen.tsx

@@ -40,10 +40,10 @@ export function StreakScreen() {
 
   return (
     <Screen>
-      <ScreenHeader title="زنجیره‌ی روزها" subtitle="هر روز حداقل یه درس، زنجیره‌ت رو زنده نگه می‌داره" color="#FF7A3D" back mascot={{ char: 'delta', mood: 'excited', size: 56 }} />
+      <ScreenHeader title="زنجیره‌ی روزها" subtitle="هر روز حداقل یه درس، زنجیره‌ت رو زنده نگه می‌داره" color="#FF7A3D" back mascot={{ mood: 'excited', size: 56 }} />
       <ScreenBody className="flex flex-col gap-4">
         {calendar.loading ? (
-          <LoadingState char="delta" />
+          <LoadingState />
         ) : calendar.error || !calendar.data ? (
           <ErrorState error={calendar.error} onRetry={calendar.reload} />
         ) : (