Export a design's timeline as a replayable command script (#1045)

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]>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -14,6 +14,8 @@ What did you expect, and what happened instead?
 
 Include steps, SolidCraft version/commit and relevant environment details. Prefer a small example without private design data.
 
+When the problem shows on a particular design, `solidcraft-cli script design.solidcraft --out repro.json` turns its history into a script that `solidcraft-cli eval repro.json` replays; attach it, trimmed to the failing step if you can.
+
 ## Screenshots of the behavior (when observable)
 
 For observable CAD, UI or model behavior, include actual descriptive screenshots or a short recording from a small reproduction. This includes kernel, geometry, assembly and backend effects that can be shown in the app. Coding agents should run the app and capture the evidence themselves, rather than asking a human for evidence they can produce. Show the actual failure/result, preferably before and after, with brief steps, expected/actual behavior and annotations where helpful.