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/panel/tool/tool.cpp

@@ -32,26 +32,26 @@ ToolPanel::ToolPanel()
 {
 	Toolbar *t = new Toolbar(this);
 
-	t->SetTool(Core::instance()->tool());
-	t->SetSnapping(Core::instance()->snapping());
+	t->set_tool(Core::instance()->tool());
+	t->set_snapping(Core::instance()->snapping());
 
-	SetWidgetWithPadding(t);
+	set_widget_with_padding(t);
 
-	connect(t, &Toolbar::ToolChanged, Core::instance(), &Core::SetTool);
-	connect(Core::instance(), &Core::ToolChanged, t, &Toolbar::SetTool);
+	connect(t, &Toolbar::tool_changed, Core::instance(), &Core::set_tool);
+	connect(Core::instance(), &Core::tool_changed, t, &Toolbar::set_tool);
 
-	connect(t, &Toolbar::SnappingChanged, Core::instance(), &Core::SetSnapping);
-	connect(Core::instance(), &Core::SnappingChanged, t, &Toolbar::SetSnapping);
+	connect(t, &Toolbar::snapping_changed, Core::instance(), &Core::set_snapping);
+	connect(Core::instance(), &Core::snapping_changed, t, &Toolbar::set_snapping);
 
-	connect(t, &Toolbar::SelectedTransitionChanged, Core::instance(),
-			&Core::SetSelectedTransitionObject);
+	connect(t, &Toolbar::selected_transition_changed, Core::instance(),
+			&Core::set_selected_transition_object);
 
-	Retranslate();
+	retranslate();
 }
 
-void ToolPanel::Retranslate()
+void ToolPanel::retranslate()
 {
-	SetTitle(tr("Tools"));
+	set_title(tr("Tools"));
 }
 
 }

app/panel/tool/tool.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef TOOL_PANEL_H
-#define TOOL_PANEL_H
+#ifndef OAK_TOOL_PANEL_H
+#define OAK_TOOL_PANEL_H
 
 #include "panel/panel.h"
 
@@ -36,9 +36,9 @@ public:
 	ToolPanel();
 
 private:
-	virtual void Retranslate() override;
+	virtual void retranslate() override;
 };
 
 }
 
-#endif // TOOL_PANEL_H
+#endif // OAK_TOOL_PANEL_H