Per-segment speed — ED.14

Speed was a lab trick long before it was a slider. On the optical printer, step-printing exposed each negative frame two or three times to make slow motion; skip-printing dropped frames for fast motion. The Steenbeck let an editor crank faster or slower to find the moment, but the speed that shipped was baked into the print at the lab. ED.14 makes it a value instead: a timescale on a segment, re-derived at preview and export so nothing is baked until you ask for it.

flowchart LR
  PRESET["speed preset (0.5×…4×)"] --> OP["EditOp::SetSpeed"]
  OP --> H["edit::History.apply"]
  H --> TS["segment.timescale"]
  TS --> DUR["project length shrinks / grows\n→ filmstrip re-flows\n→ clock re-syncs (SetDuration)"]
  TS --> PREV["preview re-times for free\nvia source_time (ED.4)"]
  TS --> EXP["export re-times + pitch-corrects\naudio (ED.21)"]

Each TimelineSegment carries a timescale: a 2× segment occupies half its source span in project time, a 0.5× segment twice as much. The ClipInspector shows presets for the selected clip; choosing one runs EditOp::SetSpeed through the shared History (undoable from the trim bin). Because speed is duration-changing, the edit re-flows the filmstrip and re-syncs the playback clock — the same SetDuration path a ripple uses.