fix: wipe tower height crash triggered by H2C/A2L support (#14758)

The new "Prime-tower visits..." test from #14685 (H2C/A2L support) throws
"Coordinate outside allowed range" at random on CI, on both Windows arm64 and
Linux x86_64. It's an uninitialized read of WipeTowerData::height.

#10780 (H2D/H2S) added a second wipe tower path, generate_new(), that fills in
depth, bbx, brim_width and rib_offset but not height. The older generate() sets
height, and clear() never did, so on the generate_new path it stays garbage.

first_layer_wipe_tower_corners() passes height to get_wipe_tower_cone_base() as
R = tan(cone_angle/2) * height. The stray bytes are usually zero, so R is zero
and the slice is fine, which is why it passes most runs on every platform. When
they aren't zero the cone radius runs past ClipperLib's limit and the slice
throws. Nothing selects for it, so it just flakes around.

#14685's test is the first to exercise this path, so that's when it started
showing up.

Initializing height in clear() fixes it, same as the m_origin fix in #13712. The
BBL generate_new path has no stabilization cone, so height = 0 is right.

src/libslic3r/Print.hpp

@@ -774,6 +774,7 @@ struct WipeTowerData
         number_of_toolchanges = -1;
         depth = 0.f;
         brim_width = 0.f;
+        height = 0.f;
         rib_offset = Vec2f::Zero();
         wipe_tower_mesh_data  = std::nullopt;
     }