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/timelinewidget/timelinewidget.cpp

@@ -19,6 +19,7 @@
 
 ***/
 
+#include <utility>
 #include "timelinewidget.h"
 #include "timelinewidgetwaveformsync.h"
 
@@ -2715,7 +2716,7 @@ void TimelineWidget::cache_clips_in_out()
 
 	const TimeRange r(Rational(int(wa.in_num), int(wa.in_den)),
 					  Rational(int(wa.out_num), int(wa.out_den)));
-	for (OakEngineBlock *b : qAsConst(selected_blocks_)) {
+	for (OakEngineBlock *b : std::as_const(selected_blocks_)) {
 		if (OakEngineBlock *clip = block_as_clip(b)) {
 			if (OakEngineNode *connected = clip_connected_node(clip)) {
 				TimeRange adjusted =
@@ -2751,7 +2752,7 @@ void TimelineWidget::multicam_enabled_triggered(bool e)
 {
 	void *command = oakengine_undo_command_create_multi();
 
-	for (OakEngineBlock *b : qAsConst(selected_blocks_)) {
+	for (OakEngineBlock *b : std::as_const(selected_blocks_)) {
 		if (OakEngineBlock *c = block_as_clip(b)) {
 			OakEngineNode *viewer = oakengine_clip_get_connected_viewer(c);
 			OakEngineSequence *s = oakengine_node_is_sequence(viewer) ?
@@ -3399,7 +3400,7 @@ TimelineWidget::generate_existing_paste_map(void *clipboard)
 
 	for (int i = 0; i < node_count; i++) {
 		OakEngineNode *n = oakengine_clipboard_get_loaded_node_at(cb, i);
-		for (OakEngineBlock *b : qAsConst(this->selected_blocks_)) {
+		for (OakEngineBlock *b : std::as_const(this->selected_blocks_)) {
 			// WRAPPER-GAP: no C ABI for Node::get_context_positions(); the
 			// block's track-owning sequence is the context that matters here
 			// (blocks on a timeline always live in their sequence's context).