Expand gtest coverage across recently changed modules

Adds ~60 new unit tests covering the modules touched in recent bug-fix
passes and UI refactors:

- RenderTicket: result/finish-count semantics, empty watcher defaults,
  ticket-reuse rejection
- Preferences tabs: behavior options migrated into General/Audio tabs,
  translation context helper, audio-tab initialization
- NodeView: context management, 'Show in Parameter Editor' action wiring
- PreviewAutoCacher: construction, pause toggles, single-frame render
  cancellation, force-cache range
- SeekableWidget/TimeBasedWidget: scroll, marker editing, context reset
- OCIOLutNode: empty/missing/unsupported LUT paths, string direction
  values, file-switching regression coverage
- ProxyManager: working filename, disabled state, empty proxy fields
- Frame/VideoParams/AudioParams/Timecode/ExportFormat/ExportCodec:
  additional edge-case and enumeration coverage

Also fixes the PreferencesAudioTab test crash by initializing
AudioManager in the offscreen test environment.

All tests pass: ctest --output-on-failure

tests/gtest/render_ticket_test.cpp

@@ -0,0 +1,144 @@
+#include <gtest/gtest.h>
+
+#include <QCoreApplication>
+#include <QtTest/QSignalSpy>
+
+#include "render/renderticket.h"
+
+using namespace olive;
+
+TEST(RenderTicketWatcher, DoesNotEmitFinishedForRunningTicketSynchronously)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Start();
+
+	RenderTicketWatcher watcher;
+	QSignalSpy spy(&watcher, &RenderTicketWatcher::Finished);
+
+	watcher.SetTicket(ticket);
+
+	// The ticket is still running, so the watcher must not emit Finished
+	// synchronously when SetTicket is called.
+	EXPECT_EQ(spy.count(), 0);
+
+	ticket->Finish();
+
+	// Once the ticket finishes, the watcher should emit Finished.
+	spy.wait(100);
+	EXPECT_EQ(spy.count(), 1);
+}
+
+TEST(RenderTicketWatcher, EmitsFinishedForAlreadyFinishedTicketAsynchronously)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Start();
+	ticket->Finish();
+
+	RenderTicketWatcher watcher;
+	QSignalSpy spy(&watcher, &RenderTicketWatcher::Finished);
+
+	watcher.SetTicket(ticket);
+
+	// The ticket has already finished. The watcher must not delete itself or
+	// emit Finished synchronously inside SetTicket, because the caller may still
+	// need the returned pointer. Instead it should defer the signal.
+	EXPECT_EQ(spy.count(), 0);
+	EXPECT_FALSE(watcher.GetTicket() == nullptr);
+
+	// Process the queued Finished emission.
+	QCoreApplication::processEvents();
+
+	EXPECT_EQ(spy.count(), 1);
+}
+
+TEST(RenderTicketWatcher, CancelMarksTicketAsCancelled)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Start();
+
+	RenderTicketWatcher watcher;
+	watcher.SetTicket(ticket);
+
+	EXPECT_TRUE(watcher.IsRunning());
+	EXPECT_FALSE(ticket->IsCancelled());
+
+	watcher.Cancel();
+
+	EXPECT_TRUE(ticket->IsCancelled());
+}
+
+TEST(RenderTicket, HasResultIsFalseWhileRunning)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Start();
+
+	EXPECT_TRUE(ticket->IsRunning());
+	EXPECT_FALSE(ticket->HasResult());
+}
+
+TEST(RenderTicket, FinishWithValueProvidesResult)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Start();
+	ticket->Finish(QVariant(42));
+
+	EXPECT_FALSE(ticket->IsRunning());
+	EXPECT_TRUE(ticket->HasResult());
+	EXPECT_EQ(ticket->Get().toInt(), 42);
+}
+
+TEST(RenderTicket, FinishCountIncrementsOnEachFinish)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	EXPECT_EQ(ticket->GetFinishCount(), 0);
+
+	ticket->Start();
+	ticket->Finish();
+	EXPECT_EQ(ticket->GetFinishCount(), 1);
+
+	ticket->Start();
+	ticket->Finish();
+	EXPECT_EQ(ticket->GetFinishCount(), 2);
+}
+
+TEST(RenderTicket, FinishWithoutStartIsIgnored)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Finish();
+	EXPECT_EQ(ticket->GetFinishCount(), 0);
+}
+
+TEST(RenderTicketWatcher, DelegatesGetAndHasResultToTicket)
+{
+	RenderTicketPtr ticket = std::make_shared<RenderTicket>();
+	ticket->Start();
+	ticket->Finish(QVariant(QStringLiteral("result")));
+
+	RenderTicketWatcher watcher;
+	watcher.SetTicket(ticket);
+
+	EXPECT_FALSE(watcher.IsRunning());
+	EXPECT_TRUE(watcher.HasResult());
+	EXPECT_EQ(watcher.Get().toString(), QStringLiteral("result"));
+}
+
+TEST(RenderTicketWatcher, EmptyWatcherReturnsDefaults)
+{
+	RenderTicketWatcher watcher;
+	EXPECT_FALSE(watcher.IsRunning());
+	EXPECT_FALSE(watcher.HasResult());
+	EXPECT_TRUE(watcher.Get().isNull());
+	EXPECT_EQ(watcher.GetTicket(), nullptr);
+}
+
+TEST(RenderTicketWatcher, SettingTicketTwiceIsRejected)
+{
+	RenderTicketPtr first = std::make_shared<RenderTicket>();
+	RenderTicketPtr second = std::make_shared<RenderTicket>();
+
+	RenderTicketWatcher watcher;
+	watcher.SetTicket(first);
+	watcher.SetTicket(second);
+
+	EXPECT_EQ(watcher.GetTicket(), first);
+}