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

docs/build_macos.md

@@ -90,9 +90,9 @@ brew install googletest
 
 ---
 
-## Build OpenTimelineIO (Optional)
+## Build OpenTimelineIO (Required)
 
-OpenTimelineIO enables importing/exporting timeline data in OTIO format. If you don't need OTIO support, you can skip this step.
+OpenTimelineIO enables importing/exporting timeline data in OTIO format. It is a required dependency.
 
 ```bash
 # Clone the repository
@@ -103,6 +103,7 @@ cd OpenTimelineIO
 cmake -S . -B build -G Ninja \
   -DOTIO_SHARED_LIBS=ON \
   -DOTIO_PYTHON_BINDINGS=OFF \
+  -DOTIO_FIND_IMATH=ON \
   -DCMAKE_BUILD_TYPE=Release \
   -DCMAKE_INSTALL_PREFIX="${PWD}/install"
 
@@ -127,16 +128,6 @@ cd oak
 
 ### 2. Configure with CMake
 
-Basic configuration (without OTIO):
-
-```bash
-cmake -S . -B build -G Ninja \
-  -DCMAKE_BUILD_TYPE=Release \
-  -DOCIO_LOCATION=$(brew --prefix opencolorio)
-```
-
-Configuration with OTIO support:
-
 ```bash
 cmake -S . -B build -G Ninja \
   -DCMAKE_BUILD_TYPE=Release \
@@ -188,7 +179,7 @@ ctest --test-dir build --output-on-failure -C Release
 | `BUILD_TESTS` | `OFF` | Build unit tests |
 | `BUILD_DOXYGEN` | `OFF` | Build Doxygen documentation |
 | `USE_WERROR` | `OFF` | Treat warnings as errors |
-| `OTIO_LOCATION` | - | Path to OpenTimelineIO installation (optional) |
+| `OTIO_LOCATION` | - | Path to OpenTimelineIO installation (required) |
 | `OCIO_LOCATION` | - | Path to OpenColorIO installation |
 
 ---