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).

CMakeLists.txt

@@ -255,11 +255,19 @@ endif()
 
 # OTIO's macOS dylibs use @loader_path install names: every binary that
 # (transitively) links them needs a copy of the dylibs next to itself.
+# Windows has no rpath either, so its DLLs must also sit next to each
+# executable (relying on PATH is fragile in CI shells).
 # Call oak_copy_otio_runtime(<target>) for each executable/shared library.
-if (OAK_BUNDLE_OTIO AND APPLE AND OTIO_LIBRARY_DIR)
-  file(GLOB OAK_OTIO_DYLIBS
-    "${OTIO_LIBRARY_DIR}/libopentimelineio*.dylib"
-    "${OTIO_LIBRARY_DIR}/libopentime*.dylib")
+if (OAK_BUNDLE_OTIO AND (APPLE OR WIN32) AND OTIO_LIBRARY_DIR)
+  if (APPLE)
+    file(GLOB OAK_OTIO_DYLIBS
+      "${OTIO_LIBRARY_DIR}/libopentimelineio*.dylib"
+      "${OTIO_LIBRARY_DIR}/libopentime*.dylib")
+  else()
+    file(GLOB OAK_OTIO_DYLIBS
+      "${OTIO_LIBRARY_DIR}/libopentimelineio*.dll"
+      "${OTIO_LIBRARY_DIR}/libopentime*.dll")
+  endif()
   function(oak_copy_otio_runtime target)
     add_custom_command(TARGET ${target} POST_BUILD
       COMMAND ${CMAKE_COMMAND} -E copy_if_different
@@ -353,8 +361,10 @@ add_subdirectory(third_party/openfx/HostSupport)
 add_subdirectory(engine)
 add_subdirectory(cli)
 
-# Everything above the engine library links against it
-list(APPEND OLIVE_LIBRARIES oakengine)
+# Internal consumers (app, tests) link oakengine-obj directly instead of the
+# oakengine shared library (see app/CMakeLists.txt). Linking both breaks the
+# Windows build: the DLL import library re-defines every symbol already
+# provided by the object files (multiple definition errors at link time).
 
 add_subdirectory(app)
 add_subdirectory(worker)