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.

CONTRIBUTING.md

@@ -20,12 +20,15 @@ submitted should abide by the following standards:
   with the following project-specific exceptions and notes:
   * Indentation uses **tabs**, not spaces.
   * Documentation comments should use **Javadoc-style** (`/** ... */`) where appropriate.
-* The naming rules below are retained from the original Olive codebase:
-  * `lowercase_underscored_variable_names`
-  * `lowercase_underscored_functions()` or `SentenceCaseFunctions()`
-  * `class SentenceCaseClassesAndStructs {}`
-  * `kSentenceCaseConstants` prepended with a lowercase `k`
-  * `UPPERCASE_UNDERSCORED_MACROS` for variables or same style as functions for macro functions
-  * `class_member_variables_` end with a `_`
+* Naming rules (enforced by `readability-identifier-naming` in `.clang-tidy`):
+  * Types (`class`, `struct`, `enum`, type aliases, template parameters): `PascalCase`
+  * Functions, variables, member variables: `snake_case`
+  * Private/protected members: trailing underscore, `class_member_variables_`
+  * Constants and enum values: `snake_case` (e.g. `k_dry_run_interval`, `k_linear`); `ALL_CAPS` is reserved for macros — save the fear for things that are actually dangerous
+  * Macros: `OAK_ALL_CAPS` (project prefix), and avoid them when a constant or function will do
+  * File names: all lowercase, `mystring.h` / `mystring.cpp`
+  * Namespaces: short `snake_case`
+  * Getters: same name as the private member without the trailing underscore (`foo_` → `foo()`); setters: `set_foo()`
+  * Exception: Qt and third-party (e.g. OpenFX) virtual overrides and framework callbacks keep their original names (`paintEvent`, `getParams`, ...) — renaming them would break the override
 * 100 column limit (where it doesn't impair readability)
 * Unix line endings (only LF no CRLF)