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).

tests/gtest/common_filefunctions_test.cpp

@@ -50,7 +50,7 @@ TEST(CommonFileFunctions, GetSafeTemporaryFilename)
 	EXPECT_TRUE(first.contains(QStringLiteral(".tmp0.")));
 
 	QFile f(first);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.close();
 
 	QString second = olive::FileFunctions::get_safe_temporary_filename(base);
@@ -80,19 +80,19 @@ TEST(CommonFileFunctions, RenameFileAllowOverwrite)
 	QString to = dir.filePath(QStringLiteral("to.txt"));
 
 	QFile f(from);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.write("source");
 	f.close();
 
 	QFile t(to);
-	t.open(QIODevice::WriteOnly);
+	(void)t.open(QIODevice::WriteOnly);
 	t.write("existing");
 	t.close();
 
 	EXPECT_TRUE(olive::FileFunctions::rename_file_allow_overwrite(from, to));
 	EXPECT_FALSE(QFileInfo::exists(from));
 	QFile result(to);
-	result.open(QIODevice::ReadOnly);
+	(void)result.open(QIODevice::ReadOnly);
 	EXPECT_EQ(result.readAll(), QByteArray("source"));
 }
 
@@ -105,7 +105,7 @@ TEST(CommonFileFunctions, CanCopyDirectoryWithoutOverwriting)
 
 	QString src_file = QDir(src.path()).filePath(QStringLiteral("file.txt"));
 	QFile f(src_file);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.close();
 
 	EXPECT_TRUE(olive::FileFunctions::can_copy_directory_without_overwriting(
@@ -113,7 +113,7 @@ TEST(CommonFileFunctions, CanCopyDirectoryWithoutOverwriting)
 
 	QString dst_file = QDir(dst.path()).filePath(QStringLiteral("file.txt"));
 	QFile g(dst_file);
-	g.open(QIODevice::WriteOnly);
+	(void)g.open(QIODevice::WriteOnly);
 	g.close();
 
 	EXPECT_FALSE(olive::FileFunctions::can_copy_directory_without_overwriting(
@@ -129,7 +129,7 @@ TEST(CommonFileFunctions, CopyDirectory)
 
 	QString src_file = QDir(src.path()).filePath(QStringLiteral("file.txt"));
 	QFile f(src_file);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.write("copied");
 	f.close();
 
@@ -208,20 +208,20 @@ TEST(CommonFileFunctions, CopyDirectoryWithOverwrite)
 
 	QString src_file = QDir(src.path()).filePath(QStringLiteral("file.txt"));
 	QFile f(src_file);
-	f.open(QIODevice::WriteOnly);
+	(void)f.open(QIODevice::WriteOnly);
 	f.write("new content");
 	f.close();
 
 	QString dst_file = QDir(dst.path()).filePath(QStringLiteral("file.txt"));
 	QFile g(dst_file);
-	g.open(QIODevice::WriteOnly);
+	(void)g.open(QIODevice::WriteOnly);
 	g.write("old content");
 	g.close();
 
 	olive::FileFunctions::copy_directory(src.path(), dst.path(), true);
 
 	QFile result(dst_file);
-	result.open(QIODevice::ReadOnly);
+	(void)result.open(QIODevice::ReadOnly);
 	EXPECT_EQ(result.readAll(), QByteArray("new content"));
 }