refactor(timeline): de-Qt oaktimeline and wrap it in a pure C ABI

- de-Qt all 11 sources: markers/workarea lose QObject/signals (list
  re-sort via direct resort() call, drawing moves to the app layer),
  explicit unique_ptr ownership for marker lists and viewer's
  workarea/markers
- timeline undo command families (split/pointer/ripple/general/track)
  now hold oaknode C handles and do all graph work through the oaknode
  C ABI (no adapter layer); gaps are attached to the project graph
  before insertion, orphan handles tracked and freed
- fix the de-Qt severed Block->Track length-changed chain with a
  direct block_length_changed() call (positions were stale after
  split/trim)
- expand oaknode C API by ~20 functions needed by timeline
  (copy_in_graph, block kind/casts, connect_element, input arrays,
  tracklist family, marker/workarea borrowed outlets)
- pure C ABI in include/timeline (marker/workarea/edit, command
  factories returning OakUndoCommand), oakcommon XML get_native
  accessors
- oaknode<->oaktimeline resolve each other at runtime; standalone
  drivers link both into test binaries
- tests: oaktimeline 117, regressions oakcommon 193 / oaknode 96 /
  oakrender 42 / oakcodec 18 / oakaudio 36 all green

src/render/standalone/CMakeLists.txt

@@ -59,6 +59,15 @@ set(BUILD_TESTS OFF)
 add_subdirectory(${OAK_REPO_ROOT}/src/undo ${CMAKE_BINARY_DIR}/undo)
 add_subdirectory(${OAK_REPO_ROOT}/src/common ${CMAKE_BINARY_DIR}/common)
 add_subdirectory(${OAK_REPO_ROOT}/src/node ${CMAKE_BINARY_DIR}/node)
+
+# M4 收尾：oaknode 运行期依赖 oaktimeline（add_default_nodes ->
+# TimelineAddTrackCommand），测试二进制须链入
+set(BUILD_TESTS OFF)
+add_subdirectory(${OAK_REPO_ROOT}/src/timeline ${CMAKE_BINARY_DIR}/timeline)
+set(BUILD_TESTS ON)
+target_link_options(oaktimeline PRIVATE
+        "-undefined" "dynamic_lookup"
+)
 set(BUILD_TESTS ON)
 
 # oaknode needs its transition stubs too when built in this tree (see

src/render/tests/CMakeLists.txt

@@ -24,6 +24,7 @@ add_executable(oakrender-gtest
 )
 
 target_link_libraries(oakrender-gtest PRIVATE
+        oaktimeline
         oakrender
         oaknode
         oakcommon