fix(06-05): make AuthSplash dead-end state reachable + persist redirect guard

- CalendarShell now captures maybeRedirectToLogin() return value in meQuery.isError effect
- When the one-shot guard is exhausted (returns false), arm loginRedirectExhausted state
- Render AuthSplash state=dead-end (tap-to-retry) when guard is exhausted, not indefinite redirecting spinner
- Reset loginRedirectExhausted on successful auth (meQuery.isSuccess) for session recovery
- Add sessionStorage.clear() to beforeEach so CalendarShell tests are isolated
- RED test committed in prior commit (36ef7a0)

apps/pwa/src/components/CalendarShell.test.tsx

@@ -140,6 +140,8 @@ function renderWithClient(ui: React.ReactElement) {
 describe('CalendarShell — CAL-03 render smoke', () => {
   beforeEach(() => {
     vi.clearAllMocks()
+    // Reset the one-shot redirect guard between tests
+    sessionStorage.clear()
 
     // Default mock responses
     ;(fetchMe as Mock).mockResolvedValue({

apps/pwa/src/components/CalendarShell.tsx

@@ -88,6 +88,10 @@ export function CalendarShell({ onOpenSettings }: { onOpenSettings?: () => void
   const queryClient = useQueryClient()
   // Ref to ensure the session-expiry redirect timer fires only once per expiry
   const sessionExpiredRedirectFired = useRef(false)
+  // When the one-shot redirect guard is already exhausted (flag set from a prior
+  // navigation), maybeRedirectToLogin() returns false — arm the dead-end state so
+  // AuthSplash shows the tap-to-retry recovery instead of spinning forever (D-11).
+  const [loginRedirectExhausted, setLoginRedirectExhausted] = useState(false)
 
   // Fetch current user to build per-member color config
   const meQuery = useQuery({
@@ -195,19 +199,25 @@ export function CalendarShell({ onOpenSettings }: { onOpenSettings?: () => void
   // If this is the first failure, maybeRedirectToLogin() sets a sessionStorage
   // flag and navigates the browser to /api/login (top-level nav, no CORS block).
   // The page will unmount as the browser navigates. If the flag is already set
-  // (already bounced through login once and still failing), returns false and the
-  // existing "Sign-in required" branch below renders.
+  // (already bounced through login once and still failing), returns false — arm
+  // loginRedirectExhausted so the dead-end "Tap to try again" branch renders
+  // instead of spinning indefinitely (D-11 dead-end recovery).
   useEffect(() => {
     if (meQuery.isError) {
-      maybeRedirectToLogin()
+      const willRedirect = maybeRedirectToLogin()
+      if (!willRedirect) {
+        setLoginRedirectExhausted(true)
+      }
     }
   }, [meQuery.isError])
 
   // Clear the one-shot flag on a successful /api/me load so a later session
   // expiry can trigger another redirect instead of showing "Sign-in required".
+  // Also reset the dead-end state in case the component is reused after auth recovery.
   useEffect(() => {
     if (meQuery.isSuccess) {
       clearLoginRedirect()
+      setLoginRedirectExhausted(false)
     }
   }, [meQuery.isSuccess])
 
@@ -257,7 +267,13 @@ export function CalendarShell({ onOpenSettings }: { onOpenSettings?: () => void
   }
 
   if (meQuery.isError) {
-    // useEffect at line 196 calls maybeRedirectToLogin() — splash shows while redirect fires
+    // loginRedirectExhausted: the one-shot guard was already set (prior navigation),
+    // so maybeRedirectToLogin() returned false — show dead-end tap-to-retry (D-11).
+    // Otherwise the useEffect at line 196 already fired maybeRedirectToLogin() and
+    // the browser is navigating — show the redirecting splash while it does.
+    if (loginRedirectExhausted) {
+      return <AuthSplash state="dead-end" />
+    }
     return <AuthSplash state="redirecting" />
   }