Add kernel booleans: union, subtract and intersect for Solid3D

SolidOperation::Boolean runs synchronously, surfaces the kernel's refusal
with a plain reason and leaves the operands untouched, consumes them on
success unless keep_operands, and records one undo step. The lifecycle test
uses planar boxes with exact volumes and covers chaining, refusals, both
formats and undo; an ignored test shows a curved refusal reaching the script.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/plugin-host-model-completion-plan.md

@@ -181,3 +181,4 @@ exact queue above and update statuses with evidence after each increment.
 - Completed `Region`. `SolidOperation::RegionFromProfile` reuses the REGION command's kernel calls and `doc.solids.region` exposes it; the lifecycle test creates regions from real circle and polyline entities and covers deletion of the source, refusals, a move, both formats and undo. Along the way `create_entity` now accepts `(x, y, z)` tuples for point properties (decided from the schema's property types) and every generated float setter accepts Python ints, so `create_entity('Circle', center=(0, 0, 0), radius=5)` works. Left: booleans (release timing first), holes and open-curve merging for regions, and `Surface`.
 - Completed `Surface` for planes, extruded open profiles, isolines and rigid moves. `SurfaceFromProfile` and `Extrude` join the kernel operations (`doc.solids.surface` and `doc.solids.extrude`); `Extrude` also gives Solid3D extrusions from closed profiles, checked against analytic volumes. The test found and fixed a real bug: Surface's `kind` field silently overwrote the entity-type `kind` key in Python dicts, so it is exposed as `surface_kind`, and a new uniqueness test guards the whole catalog. Transform now accepts surfaces (a plane stays a plane; other kinds turn generic). Left: booleans (release timing first), regions with holes, and lofted, revolved, swept and NURBS surfaces. SectionSymbol is the only unmapped kind.
 - Timed booleans in a release build (details in [cadkernel-body-path.md](cadkernel-body-path.md)). A curved box-and-cylinder boolean takes about 1 to 2.2 s, overlapping spheres 0.2 s and planar operands 1 to 2 ms, against 23 s in a debug build. The kernel refuses many curved cases quickly with a reason (`Coincident`, `CutRefused`, `NoClosedForm`), including a second cut in an already drilled box. Recommendation: add a synchronous `SolidOperation::Boolean` that surfaces the refusal and leaves the operands untouched, test it with planar operands plus one ignored curved case, and note the 30 s per-script budget. No code changed in this step.
+- Implemented `SolidOperation::Boolean` and `doc.solids.union`, `subtract` and `intersect`, as recommended by the timing study. It runs synchronously, surfaces the kernel's refusal (`Coincident`, `CutRefused`, `NoClosedForm`) with a plain-language reason and the words "nothing was changed", consumes the operands unless `keep_operands`, and records one undo step. The lifecycle test uses planar boxes (millisecond cost, exact volumes, debug-safe) and an `#[ignore]` test documents a curved refusal. With this the kernel operations in the cadkernel note are all built. SectionSymbol is the only unmapped kind.