refactor(task,render): RenderTask family over a new oakrender ticket C ABI

- oakrender: new ticket family (render_frame/render_audio with finished
  callback, result frame/samples access, cancel/wait), project copier
  C API, cache get_invalidated_ranges, manager set_aggressive_gc
- oaknode: node_copy_inputs, set_value_hint_track, viewer params
  setters, video frame cache borrowed outlet, project copy_settings
- oakcodec: encoder desired pixel format, export format extension,
  encoding generate_matrix, custom range in encoding params POD
- oaktask: RenderTask orchestrates oakrender tickets (no Qt threads/
  watchers), PreCacheTask and ExportTask rewritten over the oaknode/
  oakrender/oakcodec C ABIs; frames cross from oakrender to oakcodec
  handles by pixel copy (different control blocks)
- the two-step texture/download render path collapses into single-step
  (tickets always yield frames); subtitle sidecar kept
- tests: 105 in build-oaktask (export/precache factory paths,
  construction, conform end-to-end); regressions all green

src/task/tests/task_test.cpp

@@ -314,3 +314,51 @@ TEST(OakTaskConform, SubmittedConformProducesPcm)
 }
 
 } // namespace
+
+// ---- render family factories ----------------------------------------------
+
+TEST(OakTaskRenderFamily, FactoryErrorPaths)
+{
+	EXPECT_EQ(oaktask_create_precache(nullptr, 0, nullptr), nullptr);
+
+	oakcodec_encoding_params params = {};
+	EXPECT_EQ(oaktask_create_export(nullptr, nullptr, &params), nullptr);
+	EXPECT_EQ(oaktask_create_export(nullptr, nullptr, nullptr), nullptr);
+}
+
+TEST(OakTaskRenderFamily, ExportTaskConstruction)
+{
+	OakNodeProject *project = oaknode_project_init();
+	ASSERT_NE(project, nullptr);
+	ASSERT_EQ(oaknode_project_initialize(project), OAKNODE_OK);
+
+	// A sequence gives us a viewer with tracks; the factory should wrap
+	// the task successfully (no render manager needed for construction)
+	OakNodeSequence *sequence = oaknode_sequence_create();
+	ASSERT_NE(sequence, nullptr);
+	ASSERT_EQ(oaknode_project_add_node(project,
+									   oaknode_sequence_as_node(sequence)),
+			  OAKNODE_OK);
+
+	OakNodeColorManager *cm = oaknode_colormanager_init(project);
+	ASSERT_NE(cm, nullptr);
+
+	oakcodec_encoding_params params = {};
+	strncpy(params.filename, "/tmp/oaktask_export_test.mp4",
+			sizeof(params.filename) - 1);
+	params.video_enabled = 1;
+
+	OakTaskTask *t = oaktask_create_export(
+		oaknode_sequence_as_node(sequence), cm, &params);
+	ASSERT_NE(t, nullptr);
+
+	char title[128];
+	EXPECT_GT(oaktask_task_title(t, title, sizeof(title)), 0);
+
+	// Running needs a render manager; not available in this binary
+	oaktask_task_free(t);
+	oaknode_colormanager_free(cm);
+	oaknode_project_free(project);
+
+	EXPECT_EQ(oaktask_debug_alive_count(), 0);
+}