build: split the engine into liboakengine.so; worker drops the UI entirely

Physical split: app/{audio,cli,codec,common,config,node,pluginSupport,
render,task,timeline,undo,tool,shaders} plus coreengine, version and
ui/icons+colorcoding move to a new top-level engine/ tree, built as
liboakengine.so (shared). The render backends (oakgl/oakvulkan) move
with it and link the engine library instead of embedding a static
render-core subset (libolive-rendercore is gone).

- oak-render-worker now links liboakengine instead of the whole
  libolive-editor object set: 336MB -> 2.9MB, no Qt Widgets UI
- the editor links liboakengine for the engine and keeps only UI
  objects in libolive-editor
- install/packaging: GNUInstallDirs libdir on Linux, bundle copy on
  macOS, oakengine.dll staged for NSIS, AppImage validation entry
- fix backend lookup for the new layout: DynamicRenderer searched
  ../app but backends now live in engine/; a stale pre-split liboakgl
  in the build tree got dlopened instead, re-initialized and later
  destroyed the interposed engine statics (full-suite segfault at
  DialogSequenceParameterTab, found via gdb watchpoint)

engine/tool/CMakeLists.txt

@@ -0,0 +1,21 @@
+# Olive - Non-Linear Video Editor
+# Copyright (C) 2022 Olive Team
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set(OLIVE_SOURCES
+        ${OLIVE_SOURCES}
+        tool/tool.h
+        PARENT_SCOPE
+)

engine/tool/tool.h

@@ -0,0 +1,164 @@
+/***
+
+  Olive - Non-Linear Video Editor
+  Copyright (C) 2022 Olive Team
+  Modifications Copyright (C) 2025 mikesolar
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+***/
+
+#ifndef OAK_TOOL_H
+#define OAK_TOOL_H
+
+#include <QCoreApplication>
+#include <QString>
+
+#include "common/define.h"
+
+namespace olive
+{
+
+class Tool {
+public:
+	/**
+   * @brief A list of tools that can be used throughout the application
+   */
+	enum Item {
+		/// No tool. This should never be set as the application tool, its only real purpose is to indicate the lack of
+		/// a tool somewhere similar to nullptr.
+		k_none,
+
+		/// Pointer tool
+		k_pointer,
+
+		/// Edit tool
+		k_edit,
+
+		/// Ripple tool
+		k_ripple,
+
+		/// Rolling tool
+		k_rolling,
+
+		/// Razor tool
+		k_razor,
+
+		/// Slip tool
+		k_slip,
+
+		/// Slide tool
+		k_slide,
+
+		/// Hand tool
+		k_hand,
+
+		/// Zoom tool
+		k_zoom,
+
+		/// Transition tool
+		k_transition,
+
+		/// Record tool
+		k_record,
+
+		/// Add tool
+		k_add,
+
+		/// Track select tool
+		k_track_select,
+
+		k_count
+	};
+
+	/**
+   * @brief Tools that can be added using the kAdd tool
+   */
+	enum AddableObject {
+		/// An empty clip
+		k_addable_empty,
+
+		/// A video clip showing a generic video placeholder
+		k_addable_bars,
+
+		/// A video clip showing a primitive shape
+		k_addable_shape,
+
+		/// A video clip with a solid connected
+		k_addable_solid,
+
+		/// A video clip with a title connected
+		k_addable_title,
+
+		/// An audio clip with a sine connected to it
+		k_addable_tone,
+
+		/// A subtitle clip
+		k_addable_subtitle,
+
+		k_addable_count
+	};
+
+	static QString get_addable_object_name(const AddableObject &a)
+	{
+		switch (a) {
+		case k_addable_empty:
+			return QCoreApplication::translate("Tool", "Empty");
+		case k_addable_bars:
+			return QCoreApplication::translate("Tool", "Bars");
+		case k_addable_shape:
+			return QCoreApplication::translate("Tool", "Shape");
+		case k_addable_solid:
+			return QCoreApplication::translate("Tool", "Solid");
+		case k_addable_title:
+			return QCoreApplication::translate("Tool", "Title");
+		case k_addable_tone:
+			return QCoreApplication::translate("Tool", "Tone");
+		case k_addable_subtitle:
+			return QCoreApplication::translate("Tool", "Subtitle");
+		case k_addable_count:
+			break;
+		}
+
+		return QCoreApplication::translate("Tool", "Unknown");
+	}
+
+	static QString get_addable_object_id(const AddableObject &a)
+	{
+		switch (a) {
+		case k_addable_empty:
+			return QStringLiteral("empty");
+		case k_addable_bars:
+			return QStringLiteral("bars");
+		case k_addable_shape:
+			return QStringLiteral("shape");
+		case k_addable_solid:
+			return QStringLiteral("solid");
+		case k_addable_title:
+			return QStringLiteral("title");
+		case k_addable_tone:
+			return QStringLiteral("tone");
+		case k_addable_subtitle:
+			return QStringLiteral("subtitle");
+		case k_addable_count:
+			break;
+		}
+
+		return QString();
+	}
+};
+
+}
+
+#endif // OAK_TOOL_H