- new facade API: set_input_at_time (element addressing, track=-1 for
all components at once), set_input_string_at_time, frame_time_base,
array_insert_at/remove_at, disconnect_ex (element-aware), and
keyframes_set_type_many (first cross-track keyframe op, addressed by
(time,track) pairs)
- the widget bridge's commit funnel, color path, array ops, label
disconnect, and keyframe set-type actions in keyframeview/curvewidget
now go through the facade; keyframeviewundo.h loses two consumers
- deliberate leftovers with rationale: keyframecontrol's multi-track
composite ops (documented track-0-only limitation of the keyframe
family), keyframeproperties dialog (needs a set_time primitive),
curveview's drag UX, and NodeInputDragger (already engine-side)