R8: finish app/ pure C ABI migration (P3-P9) and make OTIO required

- app/ no longer includes engine C++ headers nor holds engine C++ types:
  engine access goes through the oakengine C ABI plus C++ wrappers
  (oakutil/oaknode.h, oakutil/oakvideo.h) and app-local mirror types
  (tooltypes, trackreferencehandle, timelinecommonapp, keyframetypes,
  subtitleapp, serializedlayoutinfoapp, nodevaluehandle, sliderdisplaytypeapp)
- engine: new C ABI functions for block/track/clip/transition navigation
  and predicates, links, caches, waveform/playback, disk folder,
  sequence_track_list, node_free, footage_is_valid, block_get_track,
  get_brush; loadotio/saveotio ported to the current engine API
- OTIO is now a required dependency: CI and CD build it on every
  platform, FindOpenTimelineIO fixed for OTIO 0.16/0.19 (the old deps
  include requirement silently disabled OTIO everywhere), runtime
  libraries are bundled into packages and copied next to macOS binaries
  (oak_copy_otio_runtime)
- fix ProjectViewModel drag&drop mime read/write size mismatch (segfault)
- unify color label naming (k_olive -> "Oak") in the app-side mirror
- docs: OTIO required, FFmpeg minimum corrected to 6.0 (en/zh)
- gtest suite: 1925 passed, 0 failed

app/widget/timelinewidget/tool/record.cpp

@@ -19,6 +19,7 @@
 #include "record.h"
 
 #include "widget/timelinewidget/timelinewidget.h"
+#include "widget/timelinewidget/trackhandle.h"
 
 namespace olive
 {
@@ -31,15 +32,18 @@ RecordTool::RecordTool(TimelineWidget *parent)
 
 void RecordTool::mouse_press(TimelineViewMouseEvent *event)
 {
-	const Track::Reference &track = event->get_track();
+	const TrackReference &track = event->get_track();
 
 	// Check if track is locked
-	Track *t = parent()->get_track_from_reference(track);
-	if (t && t->is_locked()) {
+	// TimelineWidget::get_track_from_reference() takes the app
+	// TrackReference mirror (ordinals static_assert-pinned to the engine
+	// Track::Type values, see common/trackreferencehandle.h).
+	OakEngineTrack *t = parent()->get_track_from_reference(track);
+	if (track_is_locked(t)) {
 		return;
 	}
 
-	if (t && t->type() != Track::k_audio) {
+	if (t && oakengine_track_type(t) != TrackReference::k_audio) {
 		// We only support audio tracks here
 		return;
 	}