fix(explode): correct arc/ellipse direction in mirrored INSERT blocks

Mirrored INSERTs reverse OCS handedness, but acadrust's explode used to
keep the original normal — making CCW-around-normal arcs and ellipses
sweep the wrong way. The fix lives in acadrust 7c711e9, which flips the
new normal when det < 0 and reprojects center/major_axis/angles into the
new OCS. H7CAD's fix_mirrored_arc workaround is no longer needed.

src/scene/mod.rs

@@ -3788,7 +3788,6 @@ fn tessellate_entity(
     }
 
     if let EntityType::Insert(ins) = e {
-        let is_mirrored = ins.x_scale() * ins.y_scale() < 0.0;
         // Resolve the INSERT's own style so ByBlock sub-entities can inherit it.
         let (ins_color, ins_pat_len, ins_pat, ins_lw_px, _) = render::render_style_for(document, e);
         let ins_color = render::adapt_to_bg(ins_color, bg_color);
@@ -3797,7 +3796,6 @@ fn tessellate_entity(
             .iter()
             .cloned()
             .map(crate::modules::home::modify::explode::normalize_insert_entity)
-            .map(|sub| crate::modules::home::modify::explode::fix_mirrored_arc(sub, is_mirrored))
             .flat_map(|sub| {
                 let (sub_color, sub_pattern_length, sub_pattern, sub_line_weight_px, sub_aci) =
                     render::render_style_for_block_sub(