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 <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>

CONTRIBUTING.md

@@ -119,7 +119,7 @@ the most complete description of the house style.
 |---|---|---|
 | Unit and engine tests | next to the code, or `*_tests.rs` files | `cargo xtask test` (or `cargo test --workspace --profile ci`) |
 | UI scenarios | `crates/ui-egui/tests/scenarios/*.json` | part of `cargo test` |
-| Fusion oracle | `cargo xtask oracle` | needs the local oracle data (see below) |
+| Reference tests | `cargo xtask oracle` | `tests/oracle/` (see below) |
 
 **UI scenarios** drive the real app headless: start a tool, click a plane or a sketch point,
 press keys, then assert on the result.
@@ -150,11 +150,15 @@ in the PR. `cargo xtask test` builds the tests with it and then runs every test
 `cargo xtask test -- shell`. Tests run beside each other on a busy machine, so a test must not
 depend on wall-clock timing.
 
-**The Fusion oracle** is a set of 76 reference parts, each built in Fusion from a recipe.
-SolidCraft rebuilds the same recipe and compares volume, area and topology counts with Fusion's
-measurements; [docs/oracle.md](docs/oracle.md) has the current results. The recipes and
-measurements live outside the repo (`plan/`, gitignored), because they come from a Fusion
-install. If you work on geometry and want to check against it, ask in an issue.
+**The reference tests** are 76 parts in [`tests/oracle/`](tests/oracle/), each a `recipe.json`
+in our own format with an `expected.json` beside it. SolidCraft rebuilds the recipe and compares
+body count, volume, area, centre of mass and bounding box (and, where there is a `reference.stl`,
+the surface itself). Expected values are either worked out in closed form
+(`tools/oracle-analytic/`) or computed by building the same recipe in FreeCAD, run as a separate
+program (`tools/freecad-oracle/`); each file says which. [docs/oracle.md](docs/oracle.md) has
+the current results, and CI runs `cargo xtask oracle` on every pull request. A case that fails
+because of a known bug names its issue in `expected.json` (`"known_failure": "#123"`); never
+change an expected value to match SolidCraft's output.
 
 ## Sending a change