timeline.export_script (and solidcraft-cli script) writes a design's history as a command script that solidcraft-cli eval replays into the same design, so a bug that only shows on one design becomes a one-file repro. timeline.add restores one stored feature with its id, names and references, through the same checks a design file gets when it opens.
Closes#886. SychPL's #1078 approached the same issue independently; thanks to both.
Co-authored-by: SychPL <[email protected]>
