[DlgCreateGame] Heap-allocate create game dialog to prevent crash on parent deletion (#7777)

* [DlgCreateGame] Heap-allocate create game dialog to prevent crash on parent deletion

* [Tests] Run the short-write cases without forking a death test

The three cases that force a write failure - CardDatabaseTest.Xml4ShortWriteKeepsInstalledFile,
OracleDatabaseWriter.ShortWriteKeepsPreviouslyInstalledDatabase and
SpoilerFileTest.ShortWriteLeavesExistingFileIntact - all forked a child, lowered
RLIMIT_FSIZE and ignored SIGXFSZ. That child is killed by SIGSEGV on the macOS
runners, so all three have been red on every macOS leg of master since they landed,
while the same cases pass on Linux.

Cap the soft limit in the test process instead: ctest already runs one case per
process, and the guard restores the limit and the SIGXFSZ handler, so a whole binary
keeps working. Same real EFBIG failure, no fork, and macOS keeps its coverage of the
writers.

* [CI] Derive DEBUG_TEST and RUN_TESTS in the nightly job

The shared steps gate on both, but build-linux-nightly never set them, so its
coverage leg skipped "Build debug and test" and then failed collecting a report
from an empty build/ directory on every nightly and tag run. continue-on-error
kept the run green, so the coverage artifact silently never existed.

Derive both exactly as the pull request job does.

---------

Co-authored-by: sentry[bot] <39604003+sentry[bot]@users.noreply.github.com>
Co-authored-by: Lukas Brübach <44814898+BruebachL@users.noreply.github.com>

tests/oracle/oracle_importer_test.cpp

@@ -1,6 +1,7 @@
 #include "../../oracle/src/database_writer.h"
 #include "../../oracle/src/oracleimporter.h"
 #include "../../oracle/src/raw_json_scanner.h"
+#include "../support/scoped_file_size_limit.h"
 #include "libcockatrice/card/card_info.h"
 
 #include "gtest/gtest.h"
@@ -33,12 +34,6 @@
 #include <string>
 #include <utility>
 
-#ifdef Q_OS_UNIX
-#include <csignal>
-#include <sys/resource.h>
-#include <unistd.h>
-#endif
-
 class OracleImporterTest : public ::testing::Test
 {
 protected:
@@ -1336,20 +1331,16 @@ TEST(OracleDatabaseWriter, ShortWriteKeepsPreviouslyInstalledDatabase)
     original.close();
     const QByteArray data = "<cockatrice_carddatabase version=\"4\"><!--" + QByteArray(16384, 'x') +
                             "--><cards/></cockatrice_carddatabase>";
-    // A real filesystem write failure, isolated in the death-test child so the
-    // process-wide file limit never affects other cases or the parent runner.
-    ASSERT_EXIT(
-        {
-            std::signal(SIGXFSZ, SIG_IGN);
-            struct rlimit limit;
-            limit.rlim_cur = 128;
-            limit.rlim_max = 128;
-            if (setrlimit(RLIMIT_FSIZE, &limit) != 0) {
-                _exit(2);
-            }
-            _exit(OracleDatabase::saveXml(path, data) ? 1 : 0);
-        },
-        ::testing::ExitedWithCode(0), "");
+    // A real filesystem write failure: the soft file-size cap makes the writer's own
+    // flush fail without filling a disk. The cap is scoped rather than forked, because a
+    // death-test child under RLIMIT_FSIZE is killed by SIGSEGV on macOS.
+    test_support::ScopedFileSizeLimit fileSizeCap(128);
+    ASSERT_TRUE(fileSizeCap.isValid());
+
+    QString error;
+    EXPECT_FALSE(OracleDatabase::saveXml(path, data, &error));
+    EXPECT_FALSE(error.isEmpty());
+
     ASSERT_TRUE(original.open(QIODevice::ReadOnly));
     EXPECT_EQ(original.readAll(), "installed database");
 }