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

include/render/cache.h

@@ -107,6 +107,20 @@ int oakrender_cache_has_validated_ranges(const OakRenderCache *cache);
  */
 int oakrender_cache_indicator_height(void);
 
+/**
+ * @brief The invalidated sub-ranges of [in, out) as flat
+ *        {in_n, in_d, out_n, out_d} quadruples
+ *        (PlaybackCache::get_invalidated_ranges()).
+ *
+ * Two-stage: call with ranges == NULL (or max_ranges == 0) to get the
+ * count; then call with a buffer of max_ranges * 4 int64_t values.
+ *
+ * @return Range count (>= 0), or a negative OAKRENDER_E_* code.
+ */
+int oakrender_cache_get_invalidated_ranges(OakRenderCache *c,
+		int64_t in_num, int64_t in_den, int64_t out_num, int64_t out_den,
+		int64_t *ranges, int max_ranges);
+
 /**
  * @brief Load a cached frame from disk
  * (FrameHashCache::load_cache_frame(cache_path, uuid, ts)).