engine: expose sequence video dimensions in the timeline facade

- oakengine_sequence_get_video_params (width/height/pixel aspect) with
  assertions for the default 1920x1080 square-pixel sequence and the
  invalid-handle path
- oak-cli now renders at the sequence's real dimensions instead of the
  hardcoded 1920x1080

engine/include/oakengine/timeline.h

@@ -109,6 +109,14 @@ OAKENGINE_API int
 oakengine_sequence_get_frame_rate(const OakEngineSequence *self, int *num,
 								  int *den);
 
+/**
+ * @brief Sequence video dimensions and pixel aspect ratio
+ * (ViewerOutput::get_video_params()). Any output pointer may be NULL.
+ */
+OAKENGINE_API int
+oakengine_sequence_get_video_params(const OakEngineSequence *self, int *width,
+									int *height, int *par_num, int *par_den);
+
 /**
  * @brief Number of tracks per track type (Sequence::track_list(type)->
  * get_track_count()). Any of `video`/`audio`/`subtitle` may be NULL.

engine/src/capi/timeline.cpp

@@ -191,6 +191,30 @@ int oakengine_sequence_get_frame_rate(const OakEngineSequence *self, int *num,
 	return OAKENGINE_OK;
 }
 
+int oakengine_sequence_get_video_params(const OakEngineSequence *self,
+										int *width, int *height, int *par_num,
+										int *par_den)
+{
+	if (!self) {
+		return OAKENGINE_E_INVALID;
+	}
+	const olive::VideoParams params = impl(self)->get_video_params();
+	if (width) {
+		*width = params.width();
+	}
+	if (height) {
+		*height = params.height();
+	}
+	const olive::Rational par = params.pixel_aspect_ratio();
+	if (par_num) {
+		*par_num = par.numerator();
+	}
+	if (par_den) {
+		*par_den = par.denominator();
+	}
+	return OAKENGINE_OK;
+}
+
 int oakengine_sequence_track_count(const OakEngineSequence *self, int *video,
 								   int *audio, int *subtitle)
 {

engine/tests/oakengine_init_test.cpp

@@ -180,6 +180,16 @@ static void test_sequence_and_save_load(void)
 	assert(oakengine_sequence_get_frame_rate(seq, &num, &den) == OAKENGINE_OK);
 	assert(num == 30000 && den == 1001);
 
+	// Default video dimensions (Config's DefaultSequenceWidth/Height) and
+	// square pixels
+	int width = -1, height = -1, par_num = -1, par_den = -1;
+	assert(oakengine_sequence_get_video_params(seq, &width, &height, &par_num,
+											   &par_den) == OAKENGINE_OK);
+	assert(width == 1920 && height == 1080);
+	assert(par_num == 1 && par_den == 1);
+	assert(oakengine_sequence_get_video_params(NULL, NULL, NULL, NULL, NULL) ==
+		   OAKENGINE_E_INVALID);
+
 	// Fresh sequences have no tracks.
 	int video = -1, audio = -1, subtitle = -1;
 	assert(oakengine_sequence_track_count(seq, &video, &audio, &subtitle) ==