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/dialog/task/task.h

@@ -19,8 +19,8 @@
 
 ***/
 
-#ifndef TASKDIALOG_H
-#define TASKDIALOG_H
+#ifndef OAK_TASKDIALOG_H
+#define OAK_TASKDIALOG_H
 
 #include "dialog/progress/progress.h"
 #include "task/task.h"
@@ -45,7 +45,7 @@ public:
    *
    * This is TRUE by default.
    */
-	void SetDestroyOnClose(bool e)
+	void set_destroy_on_close(bool e)
 	{
 		destroy_on_close_ = e;
 	}
@@ -53,7 +53,7 @@ public:
 	/**
    * @brief Returns this dialog's task
    */
-	Task *GetTask() const
+	Task *get_task() const
 	{
 		return task_;
 	}
@@ -64,9 +64,9 @@ protected:
 	virtual void closeEvent(QCloseEvent *e) override;
 
 signals:
-	void TaskSucceeded(Task *task);
+	void task_succeeded(Task *task);
 
-	void TaskFailed(Task *task);
+	void task_failed(Task *task);
 
 private:
 	Task *task_;
@@ -78,9 +78,9 @@ private:
 	bool task_finished_;
 
 private slots:
-	void TaskFinished();
+	void task_finished();
 };
 
 }
 
-#endif // TASKDIALOG_H
+#endif // OAK_TASKDIALOG_H