fix(measure): space points along a curve by distance, not by parameter

DIVIDE and MEASURE did nothing at all on an ELLIPSE or a SPLINE. Their
length function answered `0.0` for both — the `_ => 0.0` arm — and the
command reported the entity type as unsupported. On a polyline they
measured the chords and ignored the bulges, so points landed short of
where they belonged; on an arc or a circle they read the centre as world
coordinates when the entity stores it in its OCS.

All three now walk the entity's own curve, which the kernel measures
properly: closed forms where they exist, and the integral of the speed
where they do not.

A path ARRAY had the same confusion in a different place. It sampled the
path at even *parameters*, which is the same as even distances on a line
and a circle and nothing like it on an ellipse or a spline — copies
bunched up wherever the parameter ran slow. It also now closes properly:
on a closed path the last copy no longer lands on the first.

LENGTHEN measured an ellipse with a hundred and twenty-eight chords and
then bisected on that, and a spline with forty rounds of thirty-two
chords apiece. A chord sum reads short, so "current length" was already
below the true one before any delta was applied. Both now ask the kernel,
which also makes the spline case one evaluation instead of about
thirteen hundred.

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

Cargo.lock

@@ -935,7 +935,7 @@ checksum = "fc652a48c352aef3ea3aed32080501cf3ef6ed5da78602a020c991775b0aff04"
 [[package]]
 name = "cadkernel"
 version = "0.1.0"
-source = "git+https://github.com/HakanSeven12/cadkernel.git#9406868b1bedd57d121b11fc75658bf9eaa2c764"
+source = "git+https://github.com/HakanSeven12/cadkernel.git#92ef66a4e124881252d10eef066c65bd129ebddc"
 dependencies = [
  "cavalier_contours",
 ]