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/task/render/render.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef RENDERTASK_H
-#define RENDERTASK_H
+#ifndef OAK_RENDERTASK_H
+#define OAK_RENDERTASK_H
 
 #include <QtConcurrent/QtConcurrent>
 
@@ -41,25 +41,25 @@ public:
 	virtual ~RenderTask() override;
 
 protected:
-	bool Render(ColorManager *manager, const TimeRangeList &video_range,
+	bool render(ColorManager *manager, const TimeRangeList &video_range,
 				const TimeRangeList &audio_range,
 				const TimeRange &subtitle_range, RenderMode::Mode mode,
 				FrameHashCache *cache, const QSize &force_size = QSize(0, 0),
 				const QMatrix4x4 &force_matrix = QMatrix4x4(),
-				PixelFormat force_format = PixelFormat::INVALID,
+				PixelFormat force_format = PixelFormat::invalid,
 				int force_channel_count = 0,
 				ColorProcessorPtr force_color_output = nullptr,
 				const ColorTransform &force_color_transform = ColorTransform());
 
-	virtual bool DownloadFrame(QThread *thread, FramePtr frame,
-							   const rational &time);
+	virtual bool download_frame(QThread *thread, FramePtr frame,
+							   const Rational &time);
 
-	virtual bool FrameDownloaded(FramePtr frame, const rational &time) = 0;
+	virtual bool frame_downloaded(FramePtr frame, const Rational &time) = 0;
 
-	virtual bool AudioDownloaded(const TimeRange &range,
+	virtual bool audio_downloaded(const TimeRange &range,
 								 const SampleBuffer &samples) = 0;
 
-	virtual bool EncodeSubtitle(const SubtitleBlock *subtitle);
+	virtual bool encode_subtitle(const SubtitleBlock *subtitle);
 
 	ViewerOutput *viewer() const
 	{
@@ -98,12 +98,12 @@ protected:
 		finished_watcher_mutex_.unlock();
 	}
 
-	virtual bool TwoStepFrameRendering() const
+	virtual bool two_step_frame_rendering() const
 	{
 		return true;
 	}
 
-	void SetNativeProgressSignallingEnabled(bool e)
+	void set_native_progress_signalling_enabled(bool e)
 	{
 		native_progress_signalling_ = e;
 	}
@@ -111,18 +111,18 @@ protected:
 	/**
    * @brief Only valid after Render() is called
    */
-	int64_t GetTotalNumberOfFrames() const
+	int64_t get_total_number_of_frames() const
 	{
 		return total_number_of_frames_;
 	}
 
 private:
-	void PrepareWatcher(RenderTicketWatcher *watcher, QThread *thread);
+	void prepare_watcher(RenderTicketWatcher *watcher, QThread *thread);
 
-	void IncrementRunningTickets();
+	void increment_running_tickets();
 
-	void StartTicket(QThread *watcher_thread, ColorManager *manager,
-					 const rational &time, RenderMode::Mode mode,
+	void start_ticket(QThread *watcher_thread, ColorManager *manager,
+					 const Rational &time, RenderMode::Mode mode,
 					 FrameHashCache *cache, const QSize &force_size,
 					 const QMatrix4x4 &force_matrix, PixelFormat force_format,
 					 int force_channel_count,
@@ -146,9 +146,9 @@ private:
 	int64_t total_number_of_frames_;
 
 private slots:
-	void TicketDone(RenderTicketWatcher *watcher);
+	void ticket_done(RenderTicketWatcher *watcher);
 };
 
 }
 
-#endif // RENDERTASK_H
+#endif // OAK_RENDERTASK_H