chore: pick up cadcodec #47 and cadkernel #66; guard the re-align length

- acadrust 7ea4247: clamped-knot degree and MINSERT reservation fixes
  (cadcodec #47). cadkernel a0b962a: dogleg fails on a non-finite
  Jacobian (cadkernel #66) and pins the same codec rev, so one acadrust
  stays in the graph.
- The axis re-alignment from #1361 retains its transformed length through
  retain_segment_length, which holds a zero-length segment with per-axis
  differences instead of a P2PDistance whose gradient is NaN there.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/scene/parametric_solve.rs

@@ -2463,8 +2463,7 @@ fn solve_scope(
                     let dy = store.get(line.p2.y) - store.get(line.p1.y);
                     (dx * dx + dy * dy).sqrt()
                 };
-                let target = sys.add_param(length, true);
-                sys.add_constraint(Rc::new(P2PDistance::new(line.p1, line.p2, target)));
+                retain_segment_length(&mut sys, line.p1, line.p2, length, length);
             }
         }
         let temporary = ParametricConstraint {