refactor(codec): de-Qt oakcodec and wrap it in a pure C ABI; switch common handles to refcounted value structs

- oakcodec: de-Qt all 20 sources (QThread decode loop -> std::thread,
  QObject/signals -> callbacks), pure C ABI in include/codec with
  refcounted neutral handles (OakFrame/OakDecoder/OakEncoder),
  framemanager moved in from render, frame_to_buffer/buffer_to_frame
  moved in from oakcommon oiioutils, codec->task via submit callback
  (M8 will register), all cross-module calls go through the other
  side's C API, -fvisibility=hidden + OAKCODEC_API
- oakcommon: handles become refcounted value structs
  {ctx, addref, release, abi_version} (FFmpeg-style), pass-by-value
  signatures, free() as release wrapper; init_from_native/get_native
  for copyable value objects; OakCommonXxx renamed to OakXxx
- oakcommon: add logging (log_debug/info/warning/critical with level
  filtering and sink injection) + printf-style oakcommon_log C wrapper
- oakrender: add CancelAtom C API family; complete
  oakrender_color_processor_convert_frame; fix get_processor() missing
  definition and OCIO env var lookup
- tests: oakcommon 174, oaknode 96, oakrender 42, oakcodec 18, all
  green in their standalone builds

include/node/sequence.h

@@ -128,20 +128,24 @@ int oaknode_sequence_get_audio_stream_count(OakNodeSequence *sequence,
 											int *count);
 
 /**
- * @brief Video parameters at `index` as a NEW handle owned by the caller
- * (release with oakcommon_videoparams_free()).
+ * @brief Video parameters at `index` as a NEW by-value handle owned by
+ * the caller (reference count 1, release with
+ * oakcommon_videoparams_free()).
  *
  * @return OAKNODE_OK, OAKNODE_E_INVALID, OAKNODE_E_NOT_FOUND or
  * OAKNODE_E_NOMEM.
  */
 int oaknode_sequence_get_video_params(OakNodeSequence *sequence, int index,
-									  OakCommonVideoParams **out);
+									  OakVideoParams *out);
 
 /**
  * @brief Replace the video parameters at `index` with a copy of `params`.
+ *
+ * @return OAKNODE_E_INVALID if sequence is NULL, params.ctx is NULL, or
+ * index is negative.
  */
 int oaknode_sequence_set_video_params(OakNodeSequence *sequence, int index,
-									  const OakCommonVideoParams *params);
+									  OakVideoParams params);
 
 /**
  * @brief Audio parameters at `index` as a NEW handle owned by the caller