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/window/mainwindow/mainwindow.cpp

@@ -164,15 +164,15 @@ MainWindow::~MainWindow()
 
 void MainWindow::load_layout(const SerializedLayoutInfo &info)
 {
-	foreach (OakEngineNode *folder, info.open_folders) {
+	for (OakEngineNode *folder : info.open_folders) {
 		open_folder(folder, true);
 	}
 
-	foreach (OakEngineNode *sequence, info.open_sequences) {
+	for (OakEngineNode *sequence : info.open_sequences) {
 		open_sequence(sequence, info.open_sequences.size() == 1);
 	}
 
-	foreach (OakEngineNode *viewer, info.open_viewers) {
+	for (OakEngineNode *viewer : info.open_viewers) {
 		open_node_in_viewer(viewer);
 	}
 
@@ -470,15 +470,15 @@ void MainWindow::set_application_progress_status(ProgressStatus status)
 #if defined(Q_OS_WINDOWS)
 	if (taskbar_interface_) {
 		switch (status) {
-		case kProgressShow:
+		case k_progress_show:
 			taskbar_interface_->SetProgressState(
 				reinterpret_cast<HWND>(this->winId()), TBPF_NORMAL);
 			break;
-		case kProgressNone:
+		case k_progress_none:
 			taskbar_interface_->SetProgressState(
 				reinterpret_cast<HWND>(this->winId()), TBPF_NOPROGRESS);
 			break;
-		case kProgressError:
+		case k_progress_error:
 			taskbar_interface_->SetProgressState(
 				reinterpret_cast<HWND>(this->winId()), TBPF_ERROR);
 			break;