Sketch on a cylinder primitive's caps; format 15 (#460)

* Sketch on a cylinder primitive's caps (#420)

A solid.cylinder's caps carried no construction certificate, so a sketch
on its top or bottom was refused unless fixed:true (#420's crossed
cylinders, built from primitives).

- kernel: FaceSource::CylinderCap { producer, high, plane };
  Body::with_cylinder_certificate turns a cylinder's two extrude caps into
  certified caps. kernel::cylinder's output is unchanged for its other
  callers.
- doc: FaceCertificate::CylinderCap { high }, named F<id>:top / F<id>:bottom
  as the cylinder's face names already are; New Body and Join cylinders
  are certified, shells carry it as their planar source.
- format 15: designs can store the new certificate kind; version 14
  designs need no change, and older builds ask for an update instead of
  meeting an unknown kind.

Tests: top and bottom attachments follow a height and base edit and a
reopen; crossed joined cylinders keep both caps attachable; a shelled
cylinder's floor keeps its cap identity; malformed certificate JSON is
refused.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDDPmNdRoBgkHcLeUDKVfb

* Format 15 also covers sketch_axis links (#448)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDDPmNdRoBgkHcLeUDKVfb

---------

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

crates/doc/src/eval.rs

@@ -3643,6 +3643,7 @@ fn eval_feature(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature, st:
         }
         FeatureKind::Cylinder { base, axis, radius, height, operation } => {
             let b = kernel::cylinder(point(vals, base)?, *axis, val(vals, radius, Kind::Length)?, val(vals, height, Kind::Length)?)?;
+            let b = if matches!(operation, Operation::NewBody | Operation::Join) { b.with_cylinder_certificate(f.id)? } else { b };
             apply_traced(st, f, vec![crate::lineage::cylinder_tool(b)], *operation, &[])
         }
         FeatureKind::Sphere { center, radius, operation } => {