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/previewaudiodevice.cpp

@@ -42,16 +42,16 @@ bool PreviewAudioDevice::isSequential() const
 	return true;
 }
 
-void PreviewAudioDevice::SetParams(const core::AudioParams &params)
+void PreviewAudioDevice::set_params(const core::AudioParams &params)
 {
 	set_bytes_per_frame(params.samples_to_bytes(1));
 }
 
-qint64 PreviewAudioDevice::readData(char *data, qint64 maxSize)
+qint64 PreviewAudioDevice::readData(char *data, qint64 max_size)
 {
 	QMutexLocker locker(&lock_);
 
-	qint64 copy_length = qMin(maxSize, qint64(buffer_.size()));
+	qint64 copy_length = qMin(max_size, qint64(buffer_.size()));
 
 	if (copy_length) {
 		qint64 new_bytes_read = bytes_read_ + copy_length;
@@ -59,7 +59,7 @@ qint64 PreviewAudioDevice::readData(char *data, qint64 maxSize)
 		if (notify_interval_ > 0) {
 			if ((bytes_read_ / notify_interval_) !=
 				(new_bytes_read / notify_interval_)) {
-				emit Notify();
+				emit notify();
 			}
 		}