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/timeline/timelineworkarea.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef TIMELINEWORKAREA_H
-#define TIMELINEWORKAREA_H
+#ifndef OAK_TIMELINEWORKAREA_H
+#define OAK_TIMELINEWORKAREA_H
 
 #include <olive/core/core.h>
 #include <QObject>
@@ -40,22 +40,22 @@ public:
 	bool enabled() const;
 	void set_enabled(bool e);
 
-	const rational &in() const;
-	const rational &out() const;
-	const rational &length() const;
+	const Rational &in() const;
+	const Rational &out() const;
+	const Rational &length() const;
 	const TimeRange &range() const;
 	void set_range(const TimeRange &range);
 
 	bool load(QXmlStreamReader *reader);
 	void save(QXmlStreamWriter *writer) const;
 
-	static const rational kResetIn;
-	static const rational kResetOut;
+	static const Rational k_reset_in;
+	static const Rational k_reset_out;
 
 signals:
-	void EnabledChanged(bool e);
+	void enabled_changed(bool e);
 
-	void RangeChanged(const TimeRange &r);
+	void range_changed(const TimeRange &r);
 
 private:
 	bool workarea_enabled_;
@@ -65,4 +65,4 @@ private:
 
 }
 
-#endif // TIMELINEWORKAREA_H
+#endif // OAK_TIMELINEWORKAREA_H