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]>

docs/book/src/guide/getting-started.md

@@ -121,6 +121,23 @@ rebuilds it; `run` then exits with status 1, lists the failing features and writ
 its `--out` and `--save` files, because the bodies lack what those features should have made.
 `--allow-errors` writes them anyway.
 
+A design's history turns into a script that rebuilds it, which makes a bug that only shows
+on one design a one-file reproduction:
+
+```sh
+cargo run --release -p solidcraft-cli -- script part.solidcraft --out repro.json
+cargo run --release -p solidcraft-cli -- eval repro.json               # the same part
+```
+
+The script starts with the user parameters (`parameters.add`) and the design's units, sheet
+metal and plastic rules and materials, then adds each timeline feature with `timeline.add`,
+exactly as the design file holds it: same ids, names and parameter names, so later steps
+still find the sketches and bodies they use, and a feature that failed in the design fails
+the same way. Edit a step's values to try a change, or delete the steps after a feature to
+see the design as it was there. Appearances, folders, named views and configurations are
+left out (the CLI notes which), and designs with components or joints are not supported
+yet. In the app and over MCP the same script comes from `timeline.export_script`.
+
 Units are millimetres and degrees unless an expression says otherwise (`"1 in"`, `"30 deg"`),
 and Z is up.