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/node/generator/solid/CMakeLists.txt

@@ -0,0 +1,22 @@
+# 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}
+        node/generator/solid/solid.h
+        node/generator/solid/solid.cpp
+        PARENT_SCOPE
+)

engine/node/generator/solid/solid.cpp

@@ -0,0 +1,80 @@
+/***
+
+  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/>.
+
+***/
+
+#include "solid.h"
+
+namespace olive
+{
+
+const QString SolidGenerator::k_color_input = QStringLiteral("color_in");
+
+#define super Node
+
+SolidGenerator::SolidGenerator()
+{
+	// Default to a color that isn't black
+	add_input(k_color_input, NodeValue::k_color,
+			 QVariant::fromValue(Color(1.0f, 0.0f, 0.0f, 1.0f)));
+}
+
+QString SolidGenerator::name() const
+{
+	return tr("Solid");
+}
+
+QString SolidGenerator::id() const
+{
+	return QStringLiteral("org.olivevideoeditor.Olive.solidgenerator");
+}
+
+QVector<Node::CategoryID> SolidGenerator::category() const
+{
+	return { k_category_generator };
+}
+
+QString SolidGenerator::description() const
+{
+	return tr("Generate a solid color.");
+}
+
+void SolidGenerator::retranslate()
+{
+	super::retranslate();
+
+	set_input_name(k_color_input, tr("Color"));
+}
+
+void SolidGenerator::value(const NodeValueRow &value,
+						   const NodeGlobals &globals,
+						   NodeValueTable *table) const
+{
+	table->push(NodeValue::k_texture,
+				Texture::job(globals.vparams(), ShaderJob(value)), this);
+}
+
+ShaderCode SolidGenerator::get_shader_code(const ShaderRequest &request) const
+{
+	Q_UNUSED(request)
+
+	return ShaderCode(FileFunctions::read_file_as_string(":/shaders/solid.frag"));
+}
+
+}

engine/node/generator/solid/solid.h

@@ -0,0 +1,54 @@
+/***
+
+  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_SOLIDGENERATOR_H
+#define OAK_SOLIDGENERATOR_H
+
+#include "node/node.h"
+
+namespace olive
+{
+
+class SolidGenerator : public Node {
+	Q_OBJECT
+public:
+	SolidGenerator();
+
+	NODE_DEFAULT_FUNCTIONS(SolidGenerator)
+
+	virtual QString name() const override;
+	virtual QString id() const override;
+	virtual QVector<CategoryID> category() const override;
+	virtual QString description() const override;
+
+	virtual void retranslate() override;
+
+	virtual void value(const NodeValueRow &value, const NodeGlobals &globals,
+					   NodeValueTable *table) const override;
+	virtual ShaderCode
+	get_shader_code(const ShaderRequest &request) const override;
+
+	static const QString k_color_input;
+};
+
+}
+
+#endif // OAK_SOLIDGENERATOR_H