engine: timeline panel leftover commands migrate to the facade (round 3)

- new primitives: clip_toggle_enabled (per-block flip), clip_set_linked,
  sequence_add_default_transition (config-driven, sequence timebase),
  node_set_label_many, node_set_color_label, plus observation getters
- toggle-links, default transitions, enable toggles, color labels, and
  block renaming now go through the facade; the stray empty undo entry
  from block renaming is gone along the way
- nest/multicam/waveform-sync stay as documented composites: they mix
  redo_now intermediate state, graph surgery, and app-side computation
  that a single primitive cannot express faithfully
- the timeline panel's command execution paths are now fully migrated

engine/include/oakengine/node.h

@@ -151,6 +151,33 @@ OAKENGINE_API int oakengine_node_set_label(OakEngineNode *self,
 OAKENGINE_API int oakengine_node_set_label_ex(OakEngineNode *self,
 											  const char *label, int undoable);
 
+/**
+ * @brief Set one label on several nodes at once (undoable, ONE command;
+ * olive::NodeRenameCommand with all of them, like the application's
+ * Core::label_nodes() after its rename dialog).
+ *
+ * `nodes` holds borrowed handles (the handle is the engine node pointer
+ * in this family, so the application can pass its own nodes directly).
+ * Every entry must be non-NULL. `label` may be NULL for an empty label.
+ */
+OAKENGINE_API int oakengine_node_set_label_many(OakEngineNode **nodes,
+												int count,
+												const char *label);
+
+/**
+ * @brief Set the color-label index of several nodes at once (undoable,
+ * ONE command; olive::NodeOverrideColorCommand per node, like the
+ * timeline panel's color-label menu). `nodes` holds borrowed handles.
+ */
+OAKENGINE_API int oakengine_node_set_color_label(OakEngineNode **nodes,
+												 int count, int color_index);
+
+/**
+ * @brief The node's color-label index (Node::get_override_color(); -1 =
+ * none). -1 on a NULL handle.
+ */
+OAKENGINE_API int oakengine_node_get_color_label(const OakEngineNode *self);
+
 /* ---- Input introspection ---------------------------------------------------- */
 
 /**

engine/include/oakengine/timeline.h

@@ -494,6 +494,52 @@ OAKENGINE_API int oakengine_sequence_delete_clips(
 OAKENGINE_API int oakengine_sequence_ripple_delete_range(
 	OakEngineSequence *seq, int64_t in_ts, int64_t out_ts);
 
+/**
+ * @brief Flip the enabled flag of every given clip (undoable, ONE
+ * command; olive::BlockEnableDisableCommand per clip with the inverted
+ * current state -- the timeline panel's "toggle enabled"). Returns the
+ * number of toggled clips (>= 0) or a negative code.
+ */
+OAKENGINE_API int oakengine_clip_toggle_enabled(OakEngineClip **clips,
+												int count);
+
+/**
+ * @brief Link or unlink every given clip with each other (undoable, ONE
+ * command; olive::NodeLinkManyCommand -- the timeline panel's
+ * "link/unlink clips"). `linked` != 0 links, 0 unlinks.
+ */
+OAKENGINE_API int oakengine_clip_set_linked(OakEngineClip **clips,
+											int count, int linked);
+
+/**
+ * @brief Add the configured default transitions around the given clips
+ * (undoable, ONE command;
+ * olive::TimelineAddDefaultTransitionCommand -- the timeline panel's
+ * "add default transitions").
+ *
+ * In/out transitions are created at clip boundaries that touch a gap or
+ * the sequence edge, dual transitions between adjacent selected clips;
+ * the transition node type and length come from the engine's config
+ * (DefaultVideoTransition/DefaultAudioTransition/
+ * DefaultTransitionLength), exactly like the application. The sequence's
+ * frame-rate timebase is used for the length arithmetic.
+ */
+OAKENGINE_API int oakengine_sequence_add_default_transition(
+	OakEngineSequence *seq, OakEngineClip **clips, int count);
+
+/**
+ * @brief 1 if the clip is enabled (Block::is_enabled()). 0 on a NULL
+ * handle.
+ */
+OAKENGINE_API int oakengine_clip_is_enabled(const OakEngineClip *self);
+
+/**
+ * @brief 1 if the two clips are linked (Block::are_linked()). 0 on a
+ * NULL handle.
+ */
+OAKENGINE_API int oakengine_clip_are_linked(const OakEngineClip *a,
+											const OakEngineClip *b);
+
 /**
  * @brief Delete the workarea range on every track (undoable, ONE command;
  * the application's TimelineWidget::delete_in_to_out).