refactor(hatch): take the boundary arrangement from the kernel

624 lines become 70. What went is the planar arrangement itself —
splitting segments at their crossings, welding coincident endpoints and
tracing the bounded faces of the resulting graph — which is not a
drawing-specific problem. It is the same one a B-rep boolean solves in a
face's parameter space once the intersection curves are projected into
it, so solving it in the kernel means the boolean does not arrive with a
second copy.

What stays is reading the wires, which is where the drawing's own
conventions are: NaNs separating the runs inside one WireModel, and the
double-single coordinate pair that has to be recombined before anything
is measured.

Co-Authored-By: Claude Opus 5 <[email protected]>

Cargo.lock

@@ -935,7 +935,7 @@ checksum = "fc652a48c352aef3ea3aed32080501cf3ef6ed5da78602a020c991775b0aff04"
 [[package]]
 name = "cadkernel"
 version = "0.1.0"
-source = "git+https://github.com/HakanSeven12/cadkernel.git#92ef66a4e124881252d10eef066c65bd129ebddc"
+source = "git+https://github.com/HakanSeven12/cadkernel.git#441e3c6d8a55f3a8e799ef3cbe1e0b4301d66f14"
 dependencies = [
  "cavalier_contours",
 ]