Splitting, ripple-delete + undo/redo — ED.11

The most physical act in the cutting room: lay the film on the bench, drop the razor on the frame line, and you have two pieces where there was one. Lift one piece out and push the ends together and the cut closes — a ripple. And behind both, the safety net: the trim bin, where every offcut hangs so nothing is ever final. ED.11 brings all three to the timeline — S splits the clip under the playhead, Delete lifts the selected clip and closes the gap, ⌘Z / ⌘⇧Z walk the trim bin.

flowchart LR
  K["S at the playhead"] --> OP["EditOp::Split"]
  DEL["Delete on a selection"] --> OP2["EditOp::RippleDelete"]
  OP --> H["edit::History.apply"]
  OP2 --> H
  H --> SIG["project signal updates"]
  SIG --> STRIP["filmstrip re-flows"]
  H --> DUR["SetDuration → playback clock"]
  UNDO["⌘Z"] --> H2["History.undo / redo"] --> SIG

Each edit is just an EditOp against the (proptest-verified) History from ED.2 — the UI layer is thin. resolve_history reuses the running history when it belongs to the open clip (so the undo stack survives) or starts fresh when a different clip loads; segment_project_range turns the selected clip index into the [start, end) frames a ripple deletes. The result syncs into the reactive project signal the filmstrip already renders. Nothing here touches the negative — a split divides a segment's range, a ripple drops a segment from the list.