Fix the Oracle refresh verdict and cover the parser write path

A background refresh that already installed cards.xml exited 1 when the
token save afterwards failed, so the client kept its old in-memory
database and reported the update as failed. Return the same verdict
main() already computes: a reject after the database was written is a
successful update.

Cover the writer Oracle actually uses: add a short-write death test for
CockatriceXml4Parser::saveToFile, which reverted to QFile would truncate
an installed database without any test noticing.

Route a failed background token download through reject() instead of a
modal box on a hidden wizard, which left the client waiting with no
timeout and blocked later updates. Test the first non-space byte in
place rather than copying the payload, and report an import refusal with
the importer's own message.

oracle/src/oraclewizard.cpp

@@ -143,9 +143,11 @@ void OracleWizard::reject()
 
     QWizard::reject();
     // A hidden wizard does not close the application's last visible window.
-    // Stop background refreshes explicitly so the hosting client receives failure.
+    // Stop background refreshes explicitly so the hosting client receives a verdict,
+    // using the same rule as main(): a reject after the database was written is still
+    // a successful update, only a reject that wrote nothing counts as a failure.
     if (backgroundMode) {
-        QCoreApplication::exit(1);
+        QCoreApplication::exit(hasSavedDatabase() ? 0 : 1);
     }
 }
 

oracle/src/pages.cpp

@@ -44,6 +44,7 @@
 #include <QWizard>
 #include <QtConcurrentRun>
 #include <QtGlobal>
+#include <algorithm>
 #include <cstdio>
 #include <functional>
 #include <libcockatrice/settings/personal_settings.h>
@@ -170,7 +171,12 @@ LoadSetsResult loadSetsData(const QPointer<OracleImporter> &importer, QByteArray
         break;
     }
 
-    if (data.trimmed().startsWith("<")) {
+    // Test the first non-space byte in place: trimmed() would duplicate the whole
+    // payload, which on the plain-XML path is the largest download we handle.
+    const auto firstNonSpace = std::find_if_not(data.cbegin(), data.cend(),
+                                                [](char c) { return c == ' ' || c == '\t' || c == '\n' || c == '\r'; });
+    const bool looksLikeXml = firstNonSpace != data.cend() && *firstNonSpace == '<';
+    if (looksLikeXml) {
         result.errorMessage = OracleDatabase::validateXml(data);
         if (!result.errorMessage.isEmpty()) {
             return result;
@@ -916,7 +922,10 @@ bool SaveSetsPage::validatePage()
         wizard()->xmlData.clear();
     } else if (!wizard()->importer->saveToFile(fileName, wizard()->getCardSourceUrl(),
                                                wizard()->getCardSourceVersion())) {
-        return failSave(tr("The file could not be saved to %1").arg(fileName));
+        // The importer refuses to write a database whose import did not finish, and
+        // reports the reason there; do not dress an import failure up as a disk failure.
+        const QString importError = wizard()->importer->getImportError();
+        return failSave(importError.isEmpty() ? tr("The file could not be saved to %1").arg(fileName) : importError);
     }
 
     wizard()->markDatabaseSaved();

oracle/src/pagetemplates.cpp

@@ -185,9 +185,17 @@ void SimpleDownloadFilePage::actDownloadFinished()
     }
     QNetworkReply::NetworkError errorCode = reply->error();
     if (errorCode != QNetworkReply::NoError) {
-        QMessageBox::critical(this, tr("Error"), tr("Network error: %1.").arg(reply->errorString()));
-        wizard()->enableButtons();
+        const QString message = tr("Network error: %1.").arg(reply->errorString());
         reply->deleteLater();
+        // A hidden wizard cannot show a modal box: without an explicit stop it would sit
+        // here forever and the hosting client would wait with no timeout.
+        if (wizard()->backgroundMode) {
+            qWarning() << message;
+            wizard()->reject();
+            return;
+        }
+        QMessageBox::critical(this, tr("Error"), message);
+        wizard()->enableButtons();
         return;
     }