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/render/audiowaveformcache.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef AUDIOWAVEFORMCACHE_H
-#define AUDIOWAVEFORMCACHE_H
+#ifndef OAK_AUDIOWAVEFORMCACHE_H
+#define OAK_AUDIOWAVEFORMCACHE_H
 
 #include "audio/audiovisualwaveform.h"
 #include "playbackcache.h"
@@ -33,29 +33,29 @@ class AudioWaveformCache : public PlaybackCache {
 public:
 	AudioWaveformCache(QObject *parent = nullptr);
 
-	void WriteWaveform(const TimeRange &range,
+	void write_waveform(const TimeRange &range,
 					   const TimeRangeList &valid_ranges,
 					   const AudioVisualWaveform *waveform);
 
-	const AudioParams &GetParameters() const
+	const AudioParams &get_parameters() const
 	{
 		return params_;
 	}
-	void SetParameters(const AudioParams &p)
+	void set_parameters(const AudioParams &p)
 	{
 		params_ = p;
 		waveforms_->set_channel_count(p.channel_count());
 	}
 
 	void Draw(QPainter *painter, const QRect &rect, const double &scale,
-			  const rational &start_time) const;
+			  const Rational &start_time) const;
 
 	AudioVisualWaveform::Sample
-	GetSummaryFromTime(const rational &start, const rational &length) const;
+	get_summary_from_time(const Rational &start, const Rational &length) const;
 
-	rational length() const;
+	Rational length() const;
 
-	virtual void SetPassthrough(PlaybackCache *cache) override;
+	virtual void set_passthrough(PlaybackCache *cache) override;
 
 protected:
 	virtual void InvalidateEvent(const TimeRange &range) override;
@@ -82,4 +82,4 @@ private:
 
 }
 
-#endif // AUDIOWAVEFORMCACHE_H
+#endif // OAK_AUDIOWAVEFORMCACHE_H