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/viewer/audiowaveformview.cpp

@@ -27,7 +27,6 @@
 
 #include "common/configwrapper.h"
 #include "engineeventbridge.h"
-#include "timeline/timelinecommon.h"
 #include "widget/viewer/vieweroutpututils.h"
 
 namespace olive
@@ -59,7 +58,7 @@ AudioWaveformView::AudioWaveformView(QWidget *parent)
 			this, [this](OakEngineNode *) { viewport()->update(); });
 }
 
-void AudioWaveformView::set_viewer(ViewerOutput *playback)
+void AudioWaveformView::set_viewer(OakEngineNode *playback)
 {
 	if (playback_) {
 		pool_.clear();
@@ -75,8 +74,7 @@ void AudioWaveformView::set_viewer(ViewerOutput *playback)
 
 	if (playback_) {
 		waveform_subscription_ = waveform_bridge_->subscribe(
-			reinterpret_cast<OakEngineNode *>(playback_),
-			OAKENGINE_EVENT_VIEWER_CONNECTED_WAVEFORM_CHANGED);
+			playback_, OAKENGINE_EVENT_VIEWER_CONNECTED_WAVEFORM_CHANGED);
 
 		Rational tb =
 			viewer_output_video_params(playback_).frame_rate_as_time_base();
@@ -98,7 +96,9 @@ void AudioWaveformView::drawForeground(QPainter *p, const QRectF &rect)
 		return;
 	}
 
-	const AudioWaveformCache *wave = playback_->get_connected_waveform();
+	const AudioWaveformCache *wave =
+		static_cast<const AudioWaveformCache *>(
+			oakengine_viewer_get_connected_waveform(playback_));
 	if (!wave) {
 		return;
 	}
@@ -119,7 +119,7 @@ void AudioWaveformView::drawForeground(QPainter *p, const QRectF &rect)
 	// Draw playhead
 	p->setPen(PLAYHEAD_COLOR);
 
-	int playhead_x = time_to_scene(get_viewer_node()->get_playhead());
+	int playhead_x = time_to_scene(viewer_output_playhead(get_viewer_node()));
 	p->drawLine(playhead_x, 0, playhead_x, height());
 }