Fix: MVIEW preview rectangle drawn in XZ plane instead of XY

The preview rectangle used c1.y (constant) for all four corners and
pt.z for Z instead of c1.z. Corners 3 and 4 now correctly use pt.y
(varying Y) and the constant c1.z, producing a proper XY-plane rectangle.
Fixed in both layout/mview.rs and manage/mview.rs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/layout/mview.rs

@@ -84,8 +84,8 @@ impl CadCommand for MviewCommand {
             points: vec![
                 [c1.x, c1.y, c1.z],
                 [pt.x, c1.y, c1.z],
-                [pt.x, c1.y, pt.z],
-                [c1.x, c1.y, pt.z],
+                [pt.x, pt.y, c1.z],
+                [c1.x, pt.y, c1.z],
                 [c1.x, c1.y, c1.z],
             ],
             color: WireModel::CYAN,

src/modules/manage/mview.rs

@@ -78,8 +78,8 @@ impl CadCommand for MviewCommand {
             points:         vec![
                 [c1.x, c1.y, c1.z],
                 [pt.x, c1.y, c1.z],
-                [pt.x, c1.y, pt.z],
-                [c1.x, c1.y, pt.z],
+                [pt.x, pt.y, c1.z],
+                [c1.x, pt.y, c1.z],
                 [c1.x, c1.y, c1.z],
             ],
             color:          WireModel::CYAN,