Leading-edge brim takes part in the outer-wall-first rule

The first-layer rule that prints the outer wall first when a brim is
attached to it, and the brim_type change rule that regenerates the
perimeters for it, only knew btOuterOnly.  btLeadingEdgeOnly, the belt
brim at the part's first contact, is an outer brim too.

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

src/libslic3r/PerimeterGenerator.cpp

@@ -1839,8 +1839,10 @@ void PerimeterGenerator::process_classic()
             bool is_outer_wall_first = this->config->wall_sequence == WallSequence::OuterInner;
             if (is_outer_wall_first ||
                 //BBS: always print outer wall first when there indeed has brim.
+                // btLeadingEdgeOnly is an outer brim too (a belt brim at the part's first contact).
                 (this->layer_id == 0 &&
-                    this->object_config->brim_type == BrimType::btOuterOnly &&
+                    (this->object_config->brim_type == BrimType::btOuterOnly ||
+                     this->object_config->brim_type == BrimType::btLeadingEdgeOnly) &&
                     this->object_config->brim_width.value > 0))
                 entities.reverse();
             // Orca: sandwich mode. Apply after 1st layer.

src/libslic3r/PrintObject.cpp

@@ -1373,7 +1373,10 @@ bool PrintObject::invalidate_state_by_config_options(
                 const auto* new_brim_type = new_config.option<ConfigOptionEnum<BrimType>>(opt_key);
                 //BBS: When switch to manual brim, the object must have brim, then re-generate perimeter
                 //to make the wall order of first layer to be outer-first
-                if (old_brim_type->value == btOuterOnly || new_brim_type->value == btOuterOnly)
+                // btLeadingEdgeOnly is printed as an outer brim (Brim.cpp, BeltBrim.cpp), so it
+                // takes part in the same first-layer wall order rule.
+                if (old_brim_type->value == btOuterOnly || new_brim_type->value == btOuterOnly ||
+                    old_brim_type->value == btLeadingEdgeOnly || new_brim_type->value == btLeadingEdgeOnly)
                     steps.emplace_back(posPerimeters);
             }
         } else if (