app: migrate all engine access to the C ABI facade (nm U _ZN5olive = 0)

Every app module now reaches liboakengine exclusively through
oakengine_* C calls, EngineEventBridge subscriptions and app-side
handle headers (cliphandle/keyframehandle/nodevaluehandle/oakvaluehelper).
Direct C++ command construction, engine signal connect()s, and engine
type usage in MOC-visible signatures are gone: 557 -> 0 undefined
olive:: symbols in oak-editor.

app/widget/taskview/taskview.cpp

@@ -45,7 +45,7 @@ TaskView::TaskView(QWidget *parent)
 	layout_->addStretch();
 }
 
-void TaskView::add_task(Task *t)
+void TaskView::add_task(OakEngineTask *t)
 {
 	// Create TaskViewItem (UI representation of a Task) and connect it
 	TaskViewItem *item = new TaskViewItem(t);
@@ -54,12 +54,12 @@ void TaskView::add_task(Task *t)
 	layout_->insertWidget(layout_->count() - 1, item);
 }
 
-void TaskView::task_failed(Task *t)
+void TaskView::task_failed(OakEngineTask *t)
 {
 	items_.value(t)->failed();
 }
 
-void TaskView::remove_task(Task *t)
+void TaskView::remove_task(OakEngineTask *t)
 {
 	items_.value(t)->deleteLater();
 	items_.remove(t);

app/widget/taskview/taskview.h

@@ -44,26 +44,26 @@ public:
 	TaskView(QWidget *parent);
 
 signals:
-	void task_cancelled(Task *t);
+	void task_cancelled(OakEngineTask *t);
 
 public slots:
 	/**
-   * @brief Creates a TaskViewItem, connects it to a Task, and adds it to this widget
-   *
-   * Connect this to TaskManager::TaskAdded().
-   */
-	void add_task(Task *t);
+    * @brief Creates a TaskViewItem, connects it to a Task, and adds it to this widget
+    *
+    * Connect this to TaskManager::TaskAdded().
+    */
+	void add_task(OakEngineTask *t);
 
-	void task_failed(Task *t);
+	void task_failed(OakEngineTask *t);
 
-	void remove_task(Task *t);
+	void remove_task(OakEngineTask *t);
 
 private:
 	QWidget *central_widget_;
 
 	QVBoxLayout *layout_;
 
-	QHash<Task *, TaskViewItem *> items_;
+	QHash<OakEngineTask *, TaskViewItem *> items_;
 };
 
 }

app/widget/taskview/taskviewitem.cpp

@@ -29,7 +29,7 @@
 namespace olive
 {
 
-TaskViewItem::TaskViewItem(Task *task, QWidget *parent)
+TaskViewItem::TaskViewItem(OakEngineTask *task, QWidget *parent)
 	: QFrame(parent)
 	, task_(task)
 {
@@ -41,7 +41,10 @@ TaskViewItem::TaskViewItem(Task *task, QWidget *parent)
 
 	// Create header label
 	task_name_lbl_ = new QLabel(this);
-	task_name_lbl_->setText(task_->get_title());
+	char title_buf[512];
+	title_buf[0] = '\0';
+	oakengine_task_title(task_, title_buf, sizeof(title_buf));
+	task_name_lbl_->setText(QString::fromUtf8(title_buf));
 	layout->addWidget(task_name_lbl_);
 
 	// Create center layout (combines progress bar and a cancel button)
@@ -74,10 +77,18 @@ TaskViewItem::TaskViewItem(Task *task, QWidget *parent)
 	// Set up elapsed timer
 	status_stack_->setCurrentWidget(elapsed_timer_lbl_);
 
-	// Connect to the task
-	connect(task_, &Task::started, elapsed_timer_lbl_,
-			qOverload<qint64>(&ElapsedCounterWidget::start));
-	connect(task_, &Task::progress_changed, this, &TaskViewItem::update_progress);
+	// Connect to the task via EngineEventBridge
+	bridge_ = new EngineEventBridge(this);
+	bridge_->subscribe(task_, OAKENGINE_EVENT_TASK_STARTED);
+	bridge_->subscribe(task_, OAKENGINE_EVENT_TASK_PROGRESS);
+	connect(bridge_, &EngineEventBridge::task_started, this,
+			[this](OakEngineTask *, qint64 start_time) {
+				elapsed_timer_lbl_->start(start_time);
+			});
+	connect(bridge_, &EngineEventBridge::task_progress, this,
+			[this](OakEngineTask *, double progress) {
+				update_progress(progress);
+			});
 	connect(cancel_btn_, &QPushButton::clicked, this,
 			[this] { emit task_cancelled(task_); });
 }
@@ -86,7 +97,10 @@ void TaskViewItem::failed()
 {
 	status_stack_->setCurrentWidget(task_error_lbl_);
 	task_error_lbl_->setStyleSheet("color: red");
-	task_error_lbl_->setText(tr("Error: %1").arg(task_->get_error()));
+	char err[512];
+	err[0] = '\0';
+	oakengine_task_error(task_, err, sizeof(err));
+	task_error_lbl_->setText(tr("Error: %1").arg(QString::fromUtf8(err)));
 }
 
 void TaskViewItem::update_progress(double d)

app/widget/taskview/taskviewitem.h

@@ -29,29 +29,21 @@
 #include <QWidget>
 
 #include "elapsedcounterwidget.h"
-#include "task/task.h"
+#include "engineeventbridge.h"
+#include "oakengine/task.h"
 
 namespace olive
 {
 
-/**
- * @brief A widget that visually represents the status of a Task
- *
- * The TaskViewItem widget shows a description of the Task (Task::text(), a progress bar (updated by
- * Task::ProgressChanged), the Task's status (text generated from Task::status() or Task::error()), and provides
- * a cancel button (triggering Task::Cancel()) for cancelling a Task before it finishes.
- *
- * The main entry point is SetTask() after a Task and TaskViewItem objects are created.
- */
 class TaskViewItem : public QFrame {
 	Q_OBJECT
 public:
-	TaskViewItem(Task *task, QWidget *parent = nullptr);
+	TaskViewItem(OakEngineTask *task, QWidget *parent = nullptr);
 
 	void failed();
 
 signals:
-	void task_cancelled(Task *t);
+	void task_cancelled(OakEngineTask *t);
 
 private:
 	QLabel *task_name_lbl_;
@@ -62,7 +54,9 @@ private:
 	ElapsedCounterWidget *elapsed_timer_lbl_;
 	QLabel *task_error_lbl_;
 
-	Task *task_;
+	OakEngineTask *task_;
+
+	EngineEventBridge *bridge_;
 
 private slots:
 	void update_progress(double d);