Public reference tests: analytic and FreeCAD expected values (#310)

The oracle no longer uses Fusion measurements. tests/oracle/<case>/ now holds the 76 recipes
(our own format, with recorded measurements and tool-specific fields removed) and an
expected.json per case:

- 55 analytic cases: closed-form values from tools/oracle-analytic/ (stdlib Python, formulas
  in each case's "method").
- 21 FreeCAD cases: the same recipe built with FreeCAD's public scripting API by
  tools/freecad-oracle/ (an external program, not a dependency), with a reference.stl for 20.

solvecraft-cli oracle compares body count, volume, area, centre of mass, bbox, face counts
where the geometry fixes them, and, against reference.stl, the sampled Hausdorff distance and
the principal moments (spatial.rs from #301). cargo xtask oracle reads tests/oracle, writes
docs/oracle.md with the source of each value, and supports known_failure marks for tracked
bugs. CI runs it on every PR; a manual workflow regenerates the FreeCAD values. step-corpus,
seam normalisation and the through-all emulation, which only existed to compare with Fusion,
are removed.

75/76 pass; 75-sm-bracket-holes is a known failure (#296).


Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT

Co-authored-by: bherbruck <bherbruck@herbrucks.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/book/src/dev/testing.md

@@ -13,8 +13,7 @@ profile and the wasm build check.
 | Layout tests | `crates/ui-egui/tests/ui_layout.rs`, `window_widths.rs` | panels and dialogs at every window width |
 | Design-file corpus | `apps/solvecraft-cli/tests/corpus` | every saved file version still opens and evaluates the same |
 | Kill mid-save | `apps/solvecraft-cli/tests/kill_mid_save.rs` | a save killed at any moment leaves a readable file |
-| Fusion oracle | `cargo xtask oracle` → [docs/oracle.md](oracle.md) | parts rebuilt from recipes, compared with Fusion's measurements |
-| STEP corpus | `cargo xtask step-corpus` → [docs/step-import.md](step-import.md) | STEP files from Fusion opened and measured |
+| Reference tests | `cargo xtask oracle` → [docs/oracle.md](oracle.md) | parts rebuilt from `tests/oracle/*/recipe.json`, compared with analytic or FreeCAD expected values |
 
 ## UI scenarios