style: unify identifier naming per updated conventions

Automated with clang-tidy readability-identifier-naming (config added to
.clang-tidy) plus scripted passes, per the updated rules now documented
in CONTRIBUTING.md:

- types (class/struct/enum/alias/template params): PascalCase
- functions, variables, members: snake_case (incl. rational -> Rational)
- private/protected members: trailing underscore; static member
  variables likewise (instance_, available_themes_)
- constants and enum values: snake_case (kLinear -> k_linear,
  F32P -> f32p); ALL_CAPS reserved for macros
- macros: OAK_ prefix (OLIVE_ADD_TEST/OLIVE_ASSERT/OLIVE_CONFIG ->
  OAK_ADD_TEST/OAK_ASSERT/OAK_CONFIG, GL_PREAMBLE -> OAK_GL_PREAMBLE,
  include guards -> OAK_*)
- file names: all lowercase (Current/Plugin/OliveHost/OliveClip/
  OlivePluginInstance -> current/plugin/olivehost/oliveclip/
  oliveplugininstance)
- getters share the member name sans underscore, setters set_foo()
- Qt and third-party (OpenFX) virtual overrides and framework callbacks
  keep their original names (exempt in .clang-tidy)

Manual follow-ups required where automation could not reach:
- string-based QMetaObject/SIGNAL/SLOT references updated to renamed
  methods (AddTask, CreatedFile, DeleteSpecificFile, moveSelectionUp, ...)
- macro bodies referencing renamed methods (OLIVE_CONFIG,
  NODE_DEFAULT_DESTRUCTOR, MANAGEDDISPLAYWIDGET_*)
- self-shadowing locals renamed where signals/methods became same-named
  (size_changed, worker_count, selected_items, import param, filters)
- third_party OFX member/namespace usages restored (OFX::Host::*,
  _created, _clipPrefsDirty, createInstance, clearPersistentMessage)
- STL protocol aliases restored (const_iterator) with .clang-tidy
  ignore rules; qHash overloads restored

Full build and test suite pass: ctest 4/4, ~1960 gtest cases green.

app/node/plugins/plugin.h

@@ -0,0 +1,86 @@
+/*
+ * Oak Video Editor - Non-Linear Video Editor
+ * Copyright (C) 2025 Olive CE 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/>.
+ */
+
+#ifndef OAK_PLUGIN_NODES_H
+#define OAK_PLUGIN_NODES_H
+#include "ofxhImageEffectAPI.h"
+#include "ofxhPluginCache.h"
+#include "ofxImageEffect.h"
+#include "node/node.h"
+
+namespace olive
+{
+namespace plugin
+{
+const QString k_texture_input = QStringLiteral("tex_in");
+
+class PluginNode : public olive::Node {
+public:
+	PluginNode(OFX::Host::ImageEffect::Instance *plugin);
+	~PluginNode() override;
+
+	QString name() const override;
+	QString id() const override;
+	QVector<CategoryID> category() const override;
+	QString sub_category() const override;
+	QString description() const override;
+
+	Node *copy() const override;
+	/**
+   * @brief The main processing function
+   *
+   * The node's main purpose is to take values from inputs to set values in outputs. For whatever subclass node you
+   * create, this is where the code for that goes.
+   *
+   * Note that as a video editor, the node graph has to work across time. Depending on the purpose of your node, it may
+   * output different values depending on the time, and even if not, it will likely be receiving different input
+   * depending on the time. Most of the difficult work here is handled by NodeInput::get_value() which you should pass
+   * the `time` parameter to. It will return its value (at that time, if it's keyframed), or pass the time to a
+   * corresponding output if it's connected to one. If your node doesn't directly deal with time, the default behavior
+   * of the NodeParam objects will handle everything related to it automatically.
+   */
+	void value(const NodeValueRow &value, const NodeGlobals &globals,
+			   NodeValueTable *table) const override;
+
+	/**
+   * @brief If Value() pushes a ShaderJob, this is the function that will process them.
+   */
+	virtual void process_samples(const NodeValueRow &values,
+								const SampleBuffer &input, SampleBuffer &output,
+								int index) const;
+
+	/**
+   * @brief If Value() pushes a GenerateJob, override this function for the image to create
+   *
+   * @param frame
+   *
+   * The destination buffer. It will already be allocated and ready for writing to.
+   */
+	virtual void generate_frame(FramePtr frame, const GenerateJob &job) const;
+
+private:
+	QString sub_category_;
+
+public slots:
+	void push_button_clicked(QString name);
+};
+
+}
+}
+
+#endif //PLUGIN_H