Meshing test corpus built with SolidCraft; assembly placement in open_design (#11)

* geometry: build designs from SolidCraft command scripts (feature scripts)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* geometry: place component bodies through their occurrences when opening a design

An assembly's instances were missing and moved components sat at their own origin.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* Meshing test corpus: 16 SolidCraft recipes, analytic shapes, loader and runner

modelcraft-testkit holds the corpus (tests/corpus/<name>/recipe.json run through SolidCraft's
engine, then opened as a design) and the runner binary behind cargo xtask corpus.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* docs: corpus results, test corpus architecture and the scripts feature; licences

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* corpus: measure each body once, check stage widths, simpler loader and runner

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

---------

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/geometry/Cargo.toml

@@ -17,3 +17,10 @@ solidcraft-io = { workspace = true }
 thiserror = { workspace = true }
 zip = { workspace = true }
 quick-xml = { workspace = true }
+solidcraft-engine = { workspace = true, optional = true }
+serde_json = { workspace = true, optional = true }
+
+[features]
+# Build designs from SolidCraft command scripts (`script_design`): the test corpus and tooling.
+# Off by default; the library itself only opens designs.
+scripts = ["dep:solidcraft-engine", "dep:serde_json"]