Measure: centre-to-centre for holes, diameters for circles and arcs, slot sizes (#1392) (#1419)

Measure now reads the picked item's exact shape (cylindrical faces, circular and arc edges,
sketch circles, arcs and lines, profiles, planes, points):

- A circle, hole or arc shows Ø, R and its length (circumference, or arc length and angle).
- A slot (a sketch profile, or a half-cylinder end of a slot in a solid) shows its width,
  centre-to-centre length and overall length.
- Two items where one is round measure from the centre or axis by default (axis to axis,
  axis to plane, edge or point), with the closest and farthest distances listed too; the
  panel switches between centre, min and max, and the canvas line follows.
- inspect.measure and MCP `measure` (new `items` argument) add diameter, radius,
  center_distance, min and max; existing fields are unchanged.

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

crates/engine/src/lib.rs

@@ -941,6 +941,8 @@ mod hole_matrix_tests;
 #[cfg(test)]
 mod large_assembly_tests;
 #[cfg(test)]
+mod measure_centre_tests;
+#[cfg(test)]
 mod naming_history_tests;
 #[cfg(test)]
 mod pattern_suppress_tests;