fix: prioritize registration errors over inline validations in backendValidations

Registration errors from form submission (e.g., "password too similar to
username") were being masked by stale inline validation results. The
backendValidations memo checked state.validations first, which was set
during on-blur field validation with no errors, causing it to never reach
the registrationError branch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/register/components/RegisterContext.test.tsx

@@ -322,6 +322,37 @@ describe('RegisterContext', () => {
       });
     });
 
+    it('should prioritize registrationError over validations for backendValidations', () => {
+      const { result } = renderHook(() => useRegisterContext(), { wrapper });
+
+      // Simulate inline validation (on blur) setting validations
+      act(() => {
+        result.current.setValidationsSuccess({
+          validationDecisions: {
+            password: '',
+            username: '',
+          },
+        });
+      });
+
+      expect(result.current.backendValidations).toEqual({
+        password: '',
+        username: '',
+      });
+
+      // Simulate form submission returning a registration error
+      act(() => {
+        result.current.setRegistrationError({
+          errorCode: [{ userMessage: 'validation-error' }],
+          password: [{ userMessage: 'The password is too similar to the username.' }],
+        });
+      });
+
+      expect(result.current.backendValidations).toEqual({
+        password: 'The password is too similar to the username.',
+      });
+    });
+
     it('should return null for backendValidations when neither validations nor registrationError exist', () => {
       const { result } = renderHook(() => useRegisterContext(), { wrapper });
       expect(result.current.backendValidations).toBe(null);

src/register/components/RegisterContext.tsx

@@ -139,10 +139,6 @@ export const RegisterProvider: FC<RegisterProviderProps> = ({ children }) => {
   }, []);
 
   const backendValidations = useMemo(() => {
-    if (state.validations) {
-      return state.validations.validationDecisions;
-    }
-
     if (state.registrationError && Object.keys(state.registrationError).length > 0) {
       const fields = Object.keys(state.registrationError).filter(
         (fieldName) => !(['errorCode', 'usernameSuggestions'].includes(fieldName)),
@@ -155,6 +151,10 @@ export const RegisterProvider: FC<RegisterProviderProps> = ({ children }) => {
       return validationDecisions;
     }
 
+    if (state.validations) {
+      return state.validations.validationDecisions;
+    }
+
     return null;
   }, [state.validations, state.registrationError]);