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/gizmo/draggable.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef DRAGGABLEGIZMO_H
-#define DRAGGABLEGIZMO_H
+#ifndef OAK_DRAGGABLEGIZMO_H
+#define OAK_DRAGGABLEGIZMO_H
 
 #include "gizmo.h"
 #include "node/inputdragger.h"
@@ -35,49 +35,49 @@ public:
 	/// Changes what the X/Y coordinates emitted from HandleMovement specify
 	enum DragValueBehavior {
 		/// X/Y will be the exact mouse coordinates (in sequence pixels)
-		kAbsolute,
+		k_absolute,
 
 		/// X/Y will be the movement since the last time HandleMovement was called
-		kDeltaFromPrevious,
+		k_delta_from_previous,
 
 		/// X/Y will be the movement from the start of the drag
-		kDeltaFromStart
+		k_delta_from_start
 	};
 
 	explicit DraggableGizmo(QObject *parent = nullptr);
 
-	void DragStart(const NodeValueRow &row, double abs_x, double abs_y,
-				   const olive::core::rational &time);
+	void drag_start(const NodeValueRow &row, double abs_x, double abs_y,
+				   const olive::core::Rational &time);
 
-	void DragMove(double x, double y, const Qt::KeyboardModifiers &modifiers);
+	void drag_move(double x, double y, const Qt::KeyboardModifiers &modifiers);
 
-	void DragEnd(olive::MultiUndoCommand *command);
+	void drag_end(olive::MultiUndoCommand *command);
 
-	void AddInput(const NodeKeyframeTrackReference &input)
+	void add_input(const NodeKeyframeTrackReference &input)
 	{
 		inputs_.append(input);
 		draggers_.append(NodeInputDragger());
 	}
 
-	QVector<NodeInputDragger> &GetDraggers()
+	QVector<NodeInputDragger> &get_draggers()
 	{
 		return draggers_;
 	}
 
-	DragValueBehavior GetDragValueBehavior() const
+	DragValueBehavior get_drag_value_behavior() const
 	{
 		return drag_value_behavior_;
 	}
-	void SetDragValueBehavior(DragValueBehavior d)
+	void set_drag_value_behavior(DragValueBehavior d)
 	{
 		drag_value_behavior_ = d;
 	}
 
 signals:
-	void HandleStart(const olive::NodeValueRow &row, double x, double y,
-					 const olive::core::rational &time);
+	void handle_start(const olive::NodeValueRow &row, double x, double y,
+					 const olive::core::Rational &time);
 
-	void HandleMovement(double x, double y,
+	void handle_movement(double x, double y,
 						const Qt::KeyboardModifiers &modifiers);
 
 private:
@@ -90,4 +90,4 @@ private:
 
 }
 
-#endif // DRAGGABLEGIZMO_H
+#endif // OAK_DRAGGABLEGIZMO_H