feat(slice-3): Admin shell + complete entry routing (§5.4/§6.5, PUC-6/8/9)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -1,20 +1,22 @@
 // App shell — loads the session, applies the entry-routing rule (SD-0001 §6.5), and renders
-// the matching screen. SLICE-2 covers the unauthenticated doors (Landing/SignIn) and a
-// signed-in placeholder; the real create-storefront/admin screens land in SLICE-3.
+// the matching screen. The rule is exhaustive: no state lands nowhere (BUC-4). The verify
+// response carries the same shape as /me, so onAuthed feeds the session directly.
 import { useEffect, useState } from "react";
-import { getMe, type VerifyResult } from "./api";
+import { getMe, type StorefrontResult, type VerifyResult } from "./api";
 import { routeFor, type SessionState } from "./routing";
+import Admin from "./screens/Admin";
+import CreateStorefront from "./screens/CreateStorefront";
 import Landing from "./screens/Landing";
 import SignIn from "./screens/SignIn";
-import SignedIn from "./screens/SignedIn";
 
 type Door = "signup" | "login";
+type Welcome = "new" | "back" | null;
 
 export default function App() {
   const [session, setSession] = useState<SessionState | null>(null);
   const [loading, setLoading] = useState(true);
   const [door, setDoor] = useState<Door | null>(null);
-  const [justCreated, setJustCreated] = useState(false);
+  const [welcome, setWelcome] = useState<Welcome>(null);
 
   async function reload() {
     setLoading(true);
@@ -26,7 +28,15 @@ export default function App() {
     void reload();
   }, []);
 
-  if (loading) return <main>Loading…</main>;
+  if (loading) {
+    return (
+      <div className="screen screen--plain">
+        <main className="screen__main">
+          <p className="note">Loading…</p>
+        </main>
+      </div>
+    );
+  }
 
   const route = routeFor(session ?? { account: null, storefront: null });
 
@@ -35,13 +45,11 @@ export default function App() {
       return (
         <SignIn
           door={door}
-          onBack={() => {
-            setDoor(null);
-          }}
+          onBack={() => setDoor(null)}
           onAuthed={(result: VerifyResult) => {
-            setJustCreated(result.created);
+            setWelcome(result.created ? "new" : "back");
             setDoor(null);
-            void reload();
+            setSession({ account: result.account, storefront: result.storefront });
           }}
         />
       );
@@ -49,16 +57,35 @@ export default function App() {
     return <Landing onGetStarted={() => setDoor("signup")} onLogIn={() => setDoor("login")} />;
   }
 
-  // route is "create-storefront" or "admin" — both are SLICE-3 screens; SLICE-2 shows the
-  // signed-in placeholder so sign-out (PUC-9) is reachable.
+  const email = session!.account!.email;
+
+  function signedOut() {
+    setWelcome(null);
+    setDoor(null);
+    setSession(null);
+  }
+
+  if (route === "create-storefront") {
+    return (
+      <CreateStorefront
+        email={email}
+        welcome={welcome}
+        onCreated={(sf: StorefrontResult) => {
+          setWelcome(null);
+          setSession({ account: { email }, storefront: sf });
+        }}
+        onAlreadyOwns={() => void reload()}
+        onSignedOut={signedOut}
+      />
+    );
+  }
+
   return (
-    <SignedIn
-      email={session!.account!.email}
-      created={justCreated}
-      onSignedOut={() => {
-        setJustCreated(false);
-        void reload();
-      }}
+    <Admin
+      storefrontName={session!.storefront!.name}
+      email={email}
+      welcome={welcome}
+      onSignedOut={signedOut}
     />
   );
 }