The canonical generation/preview/key splitter (split_scenes) only treated a
shortcut as a scene cut when the shortcut's TRIGGER word was a key in the
transition DB. But split markers are commonly keyed by the EXPANSION phrase: a
"cut" shortcut expands to "Scene cut.", and the split marker is "scene cut.".
So the lookup `custom_map.get(_norm(raw))` missed, the shortcut was treated as
plain content, and NO cut was made — split_scenes returned one scene for
"A cut B cut C" while the verbatim editor split returned three. That disagreement
collapsed the timeline's middle scenes (and would have generated one scene).
Fix: when the trigger word isn't in the DB, also match the shortcut's EXPANSION
(`custom_map.get(_norm(exp))`). The generic "scene <N>" label is still NOT matched
on expansions, so an incidental "scene 2" inside a content shortcut never cuts.
Verified against the user's on-disk cut/qcut defs: split_scenes now agrees with
the verbatim split (2 scenes for cut x2 / qcut x2 / mixed). Added regression tests.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
