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/keyframeview/keyframeviewinputconnection.h

@@ -22,13 +22,12 @@
 #ifndef OAK_KEYFRAMEVIEWINPUTCONNECTION_H
 #define OAK_KEYFRAMEVIEWINPUTCONNECTION_H
 
+#include <QBrush>
 #include <QObject>
+#include <QVector>
 
 #include "engineeventbridge.h"
-#include "node/node.h"
-#include "node/param.h"
-
-struct OakEngineKeyframe;
+#include "oakutil/oaknode.h"
 
 namespace olive
 {
@@ -38,7 +37,7 @@ class KeyframeView;
 class KeyframeViewInputConnection : public QObject {
 	Q_OBJECT
 public:
-	KeyframeViewInputConnection(const NodeKeyframeTrackReference &input,
+	KeyframeViewInputConnection(const oak::KeyframeTrackRef &input,
 								KeyframeView *parent);
 
 	const int &get_keyframe_y() const
@@ -52,20 +51,14 @@ public:
 
 	void set_y_behavior(YBehavior e);
 
-	const QVector<NodeKeyframe *> &get_keyframes() const
-	{
-		return input_.input()
-			.node()
-			->get_keyframe_tracks(input_.input())
-			.at(input_.track());
-	}
+	QVector<oak::Keyframe> get_keyframes() const;
 
 	const QBrush &get_brush() const
 	{
 		return brush_;
 	}
 
-	const NodeKeyframeTrackReference &get_reference() const
+	const oak::KeyframeTrackRef &get_reference() const
 	{
 		return input_;
 	}
@@ -80,7 +73,7 @@ signals:
 private:
 	KeyframeView *keyframe_view_;
 
-	NodeKeyframeTrackReference input_;
+	oak::KeyframeTrackRef input_;
 
 	int y_;