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/math/trigonometry/trigonometry.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef TRIGNODE_H
-#define TRIGNODE_H
+#ifndef OAK_TRIGNODE_H
+#define OAK_TRIGNODE_H
 
 #include "node/node.h"
 
@@ -34,33 +34,33 @@ public:
 
 	NODE_DEFAULT_FUNCTIONS(TrigonometryNode)
 
-	virtual QString Name() const override;
+	virtual QString name() const override;
 	virtual QString id() const override;
-	virtual QVector<CategoryID> Category() const override;
-	virtual QString Description() const override;
+	virtual QVector<CategoryID> category() const override;
+	virtual QString description() const override;
 
-	virtual void Retranslate() override;
+	virtual void retranslate() override;
 
-	virtual void Value(const NodeValueRow &value, const NodeGlobals &globals,
+	virtual void value(const NodeValueRow &value, const NodeGlobals &globals,
 					   NodeValueTable *table) const override;
 
-	static const QString kMethodIn;
-	static const QString kXIn;
+	static const QString k_method_in;
+	static const QString k_x_in;
 
 private:
 	enum Operation {
-		kOpSine,
-		kOpCosine,
-		kOpTangent,
-		kOpArcSine,
-		kOpArcCosine,
-		kOpArcTangent,
-		kOpHypSine,
-		kOpHypCosine,
-		kOpHypTangent
+		k_op_sine,
+		k_op_cosine,
+		k_op_tangent,
+		k_op_arc_sine,
+		k_op_arc_cosine,
+		k_op_arc_tangent,
+		k_op_hyp_sine,
+		k_op_hyp_cosine,
+		k_op_hyp_tangent
 	};
 };
 
 }
 
-#endif // TRIGNODE_H
+#endif // OAK_TRIGNODE_H