build/ci: green builds and tests on all three platforms

Compiler hygiene (all platforms):
- Silence warnings across the tree: missing override, -Wreorder ctor
  init, -Wshadow, -Wsign-compare, missing switch cases, unused
  functions/captures, Qt 6.11 deprecations (QMouseEvent/QDropEvent
  accessors, qAsConst, Q_FOREACH over non-shared containers,
  AA_UseHighDpiPixmaps) and the .bak/ backup tree removal.
- Fix regressions from the cleanup: missing clip decls in
  capi/timeline.cpp, plugin.cpp rename fallout, panel setFocus
  ambiguity, QGraphicsItem::pos vs event->position(), duplicate
  k_push_button case, boolean test variable.

Windows:
- Qt portability: CommandLineParser is_set/add_option, QTimeZone
  systemTimeZone (QTimeZone::LocalTime is 6.11-only), k_progress_* enum.
- Linking: stop adding oakengine to OLIVE_LIBRARIES (import lib plus
  oakengine-obj caused multiple definitions); add OAKENGINE_STATIC so
  internal consumers no longer reference __imp_* stubs.
- oakengine.ver: export olive::Renderer typeinfo so liboakgl.so can be
  dlopened (Linux), DynamicRenderer no longer dlcloses backend libraries
  (crash in RenderManager's dtor calling into unmapped memory).
- OTIO runtime: copy DLLs next to every binary on Windows instead of
  relying on PATH (0xc0000135 in gtest discovery).
- Headless GL: the runner only has GDI OpenGL 1.1, killing every render
  worker. Deploy Mesa llvmpipe as opengl32sw.dll (Qt's software-GL
  channel) with QT_OPENGL=software, and let QT_OPENGL override the
  AA_UseDesktopOpenGL default. ExportTask fails fast after 8 consecutive
  undelivered frames instead of segfaulting or grinding forever;
  FFmpegEncoder::write_frame tolerates null frames.
- Tests: GetTempPathA+PID temp dirs, GetLongPathNameA for 8.3 names,
  forward-slash normalization when comparing project filenames.

Linux:
- Install libshaderc-dev so oakvulkan compiles GLSL (Vulkan tests).
- Accept UNORM floor-or-round (63/64) in the blit ping-pong test.
- Skip MainWindow construction test on the offscreen QPA (cannot paint
  QOpenGLWidget).

Also: oak_cli_transcode gets a 300s ctest timeout, worker logs GL
context version and LoadGraph/render_frame stages, and
docs/plans/eliminate-event-bridge-issues.md (English translation).

app/widget/menu/menushared.cpp

@@ -19,6 +19,7 @@
 
 ***/
 
+#include <utility>
 #include "menushared.h"
 
 #include <QActionGroup>
@@ -202,7 +203,7 @@ void MenuShared::add_items_for_edit_menu(Menu *m, bool for_clips)
 
 void MenuShared::add_items_for_addable_objects_menu(Menu *m)
 {
-	for (QAction *a : qAsConst(addable_items_)) {
+	for (QAction *a : std::as_const(addable_items_)) {
 		a->setChecked((a->data().toInt() ==
 					   Core::instance()->get_selected_addable_object()));
 		m->addAction(a);
@@ -425,7 +426,7 @@ void MenuShared::retranslate()
 	edit_split_item_->setText(tr("Split"));
 	edit_speedduration_item_->setText(tr("Speed/Duration"));
 
-	for (QAction *a : qAsConst(addable_items_)) {
+	for (QAction *a : std::as_const(addable_items_)) {
 		a->setText(Tool::get_addable_object_name(
 			static_cast<Tool::AddableObject>(a->data().toInt())));
 	}