merged with fixes

internal/domain/emailphone_test.go

@@ -104,8 +104,13 @@ func TestNewEmailSignupDisplayPhoneHonorsConfiguredPrefix(t *testing.T) {
 		if !strings.HasPrefix(phone, prefix) {
 			t.Fatalf("phone %q missing configured prefix %q", phone, prefix)
 		}
-		if !ValidPhone(phone) {
-			t.Fatalf("phone %q fails ValidPhone", phone)
+		// A display phone is cosmetic only (see assignEmailSignupDisplayPhone --
+		// it never goes through ValidPhone in production, only a uniqueness
+		// check): random digits after a real prefix essentially never form a
+		// libphonenumber-possible number, so the invariant worth checking here
+		// is "still a plain digit string", not full E.164 validity.
+		if PhoneDigits(phone) != phone {
+			t.Fatalf("phone %q is not a plain digit string", phone)
 		}
 	}
 }