- Right-clicking an unselected clip selects it first (C++ parity) —
this is what made Cut/Delete appear to do nothing.
- Cut/Copy/Paste clipboard: clipboard_copy/cut/paste on the engine,
clipboard clips keep footage/range/speed/track kind and stay linked
in the pasted group; paste lands at the playhead as one undo entry.
- Dropping a video-with-audio footage places the video clip plus a
linked audio clip at the same range in ONE 'Add Clip' undo entry.
- Add Video/Audio Track buttons in the timeline toolbar and the track
header context menu; new sequences start with 2 video + 2 audio
tracks (not an undoable edit).
- oaknode Graph::add_entry now reclaims the slot from the free list —
before, a detached-then-reattached node left its slot in the free
list, so node_count undercounted and the next add_node silently
clobbered the restored node. This was the user's 'undo, redo, undo,
redo and the result changed' bug; regression covered by cycle tests
(move/trim/delete/split/add-track/linked-placement all converge).
Mike-Solar