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/widget/nodeview/nodeviewcommon.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef NODEVIEWCOMMON_H
-#define NODEVIEWCOMMON_H
+#ifndef OAK_NODEVIEWCOMMON_H
+#define OAK_NODEVIEWCOMMON_H
 
 #include <QtGlobal>
 
@@ -32,45 +32,45 @@ namespace olive
 class NodeViewCommon {
 public:
 	enum FlowDirection {
-		kInvalidDirection = -1,
-		kTopToBottom,
-		kBottomToTop,
-		kLeftToRight,
-		kRightToLeft
+		k_invalid_direction = -1,
+		k_top_to_bottom,
+		k_bottom_to_top,
+		k_left_to_right,
+		k_right_to_left
 	};
 
-	static Qt::Orientation GetFlowOrientation(FlowDirection dir)
+	static Qt::Orientation get_flow_orientation(FlowDirection dir)
 	{
-		if (dir == kTopToBottom || dir == kBottomToTop) {
+		if (dir == k_top_to_bottom || dir == k_bottom_to_top) {
 			return Qt::Vertical;
 		} else {
 			return Qt::Horizontal;
 		}
 	}
 
-	static bool IsFlowVertical(FlowDirection dir)
+	static bool is_flow_vertical(FlowDirection dir)
 	{
-		return dir == kTopToBottom || dir == kBottomToTop;
+		return dir == k_top_to_bottom || dir == k_bottom_to_top;
 	}
 
-	static bool IsFlowHorizontal(FlowDirection dir)
+	static bool is_flow_horizontal(FlowDirection dir)
 	{
-		return dir == kLeftToRight || dir == kRightToLeft;
+		return dir == k_left_to_right || dir == k_right_to_left;
 	}
 
-	static bool DirectionsAreOpposing(FlowDirection a, FlowDirection b)
+	static bool directions_are_opposing(FlowDirection a, FlowDirection b)
 	{
-		return ((a == NodeViewCommon::kLeftToRight &&
-				 b == NodeViewCommon::kRightToLeft) ||
-				(a == NodeViewCommon::kRightToLeft &&
-				 b == NodeViewCommon::kLeftToRight) ||
-				(a == NodeViewCommon::kTopToBottom &&
-				 b == NodeViewCommon::kBottomToTop) ||
-				(a == NodeViewCommon::kBottomToTop &&
-				 b == NodeViewCommon::kTopToBottom));
+		return ((a == NodeViewCommon::k_left_to_right &&
+				 b == NodeViewCommon::k_right_to_left) ||
+				(a == NodeViewCommon::k_right_to_left &&
+				 b == NodeViewCommon::k_left_to_right) ||
+				(a == NodeViewCommon::k_top_to_bottom &&
+				 b == NodeViewCommon::k_bottom_to_top) ||
+				(a == NodeViewCommon::k_bottom_to_top &&
+				 b == NodeViewCommon::k_top_to_bottom));
 	}
 };
 
 }
 
-#endif // NODEVIEWCOMMON_H
+#endif // OAK_NODEVIEWCOMMON_H