Merge upstream/main into belt/rebase/may-18

Reconciles the belt-printer branch with upstream PRs through #13723. Six
files had conflicts; three additional files needed manual follow-up fixes
where the auto-merge produced code that referenced upstream-renamed fields
or changed function signatures.

Notable reconciliations:
- TreeSupport.cpp: kept belt-floor early-exit branches around HEAD's
  drop-down logic, folded upstream's `(distance_to_top > 0 ? 1 : 0)`
  formula into the non-belt-floor path (upstream PR #11812). Dropped dead
  `roof_enabled`/`force_tip_to_roof` locals.
- TreeSupport3D.cpp: combined upstream's safety-offset + remove_small
  changes with HEAD's belt-floor clip in the per-slice trim loop. Dropped
  HEAD's `else` block (superseded by upstream's rewritten bottom-contact
  propagation) and re-added the belt-floor clip into the new propagation
  loop. Gated the propagation on belt printers to prevent OOM when
  belt-floor clipping produces empty initial slices.
- TriangleSelector.{cpp,hpp}: merged both new `select_patch` parameters
  (HEAD's `up_direction` and upstream's `select_partially`); body uses
  `dot(up_direction)` for the overhang angle check and forwards
  `select_partially` to `select_triangle`.
- SupportMaterial.cpp: `slicing_params.soluble_interface` →
  `zero_gap_interface_bottom` in HEAD's `detect_belt_floor_bottom_contacts`,
  matching upstream's same-purpose rename at line 2495.
- Custom.json, GCodeWriter.cpp: simple additive merges (kept entries /
  includes from both sides).

Verified by building OrcaSlicer (RelWithDebInfo) after a full deps
rebuild (Eigen v5.0.1, libigl v2.6.0 are now managed deps) and slicing
a scaled Benchy on the NORMALIZER belt-printer profile without OOM.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/slic3r/GUI/GUI_Factories.cpp

@@ -1235,7 +1235,7 @@ void MenuFactory::append_menu_items_convert_unit(wxMenu* menu)
 
 void MenuFactory::append_menu_item_merge_to_multipart_object(wxMenu* menu)
 {
-    append_menu_item(menu, wxID_ANY, _L("Assemble"), _L("Assemble the selected objects to an object with multiple parts"),
+    append_menu_item(menu, wxID_ANY, _L("Assemble"), _L("Assemble the selected objects into an object with multiple parts"),
         [](wxCommandEvent&) { obj_list()->merge(true); }, "", menu,
         []() { return obj_list()->can_merge_to_multipart_object(); }, m_parent);
 }
@@ -1243,7 +1243,7 @@ void MenuFactory::append_menu_item_merge_to_multipart_object(wxMenu* menu)
 void MenuFactory::append_menu_item_merge_to_single_object(wxMenu* menu)
 {
     menu->AppendSeparator();
-    append_menu_item(menu, wxID_ANY, _L("Assemble"), _L("Assemble the selected objects to an object with single part"),
+    append_menu_item(menu, wxID_ANY, _L("Assemble"), _L("Assemble the selected objects into an object with single part"),
         [](wxCommandEvent&) { obj_list()->merge(false); }, "", menu,
         []() { return obj_list()->can_merge_to_single_object(); }, m_parent);
 }
@@ -1646,17 +1646,6 @@ void MenuFactory::create_filament_action_menu(bool init, int active_filament_men
             []() { return true; }, m_parent);
     }
 
-    if (init) {
-        append_menu_item(
-            menu, wxID_ANY, _L("Delete"), _L("Delete this filament"), [](wxCommandEvent&) {
-                plater()->sidebar().delete_filament(-2); }, "", nullptr,
-            []() {
-                return plater()->sidebar().combos_filament().size() > 1
-                    // Orca: only show delete filament option for SEMM machines unless is BBL
-                    && Sidebar::should_show_SEMM_buttons();
-            }, m_parent);
-    }
-
     const int item_id = menu->FindItem(_L("Merge with"));
     if (item_id != wxNOT_FOUND)
         menu->Destroy(item_id);
@@ -1677,6 +1666,20 @@ void MenuFactory::create_filament_action_menu(bool init, int active_filament_men
     }
     append_submenu(menu, sub_menu, wxID_ANY, _L("Merge with"), "", "",
         [filaments_cnt]() { return filaments_cnt > 1; }, m_parent);
+
+    // ORCA use delete item on end of menu to prevent accidental clicks. clicking to submenus(merge) already not allowed by OS
+    const int delete_id = menu->FindItem(_L("Delete"));
+    if (delete_id != wxNOT_FOUND)
+        menu->Destroy(delete_id);
+    
+    append_menu_item(
+        menu, wxID_ANY, _L("Delete"), _L("Delete this filament"), [](wxCommandEvent&) {
+            plater()->sidebar().delete_filament(-2); }, "", nullptr,
+        []() {
+            return plater()->sidebar().combos_filament().size() > 1
+                // Orca: only show delete filament option for SEMM machines unless is BBL
+                && Sidebar::should_show_SEMM_buttons();
+        }, m_parent);
 }
 
 //BBS: add part plate related logic