Merge upstream/main into belt-printer

Brings belt-printer up to main 4b4a261787. Resolutions:

- G-code header (#15897, #15915): main moved the header, config and
  thumbnail block later in _do_export; write_belt_header() moves with it,
  still after the thumbnails and outside the BTT_TFT gate.
- _extrude: first-layer acceleration keeps the per-path first-layer plane
  test with main's cached nozzle index (#16028); main's set_speed out-param
  form (#16108) everywhere else.
- GCodeWriter (#16108): the arc-to-polyline fallback for machine mappings
  that cannot express G2/G3 now runs in the out-param extrude_arc_to_xy,
  which is the overload GCode calls, and appends to the caller's string.
- GCodeProcessorResult: the belt fields join main's forwarding assign.
- Clipper2 (#15969): belt arrange helpers take Slic3r::Point; the tree
  support join types lose their ClipperLib qualifier.
- CLI arrange (#15837): belt printers still reserve no wipe tower.
- Wipe tower options (#15841): the two new sparse-layer toggles are hidden
  for belt printers like the rest of the tower options.
- Keyboard shortcuts (#15706): main's registry replaces the old key switch;
  the belt view toggle is re-registered in the next commit.
- Print::process: the belt purge-plan undo runs before main's SliceStarted
  event.
- scripts/filament_id_snapshot.json: deleted on main (a77209af8f).
- Includes and appended tests: union of both sides.

src/slic3r/GUI/GUI_Preview.cpp

@@ -5,6 +5,23 @@
 #include "GUI_Preview.hpp"
 #include "GUI_App.hpp"
 #include "GUI.hpp"
+#include <wx/slider.h>
+#include <wx/gdicmn.h>
+#include <string>
+#include <vector>
+#include "libslic3r/GCode/GCodeProcessor.hpp"
+#include <functional>
+#include "libslic3r/Config.hpp"
+#include <boost/log/trivial.hpp>
+#include "libslic3r/CustomGCode.hpp"
+#include <wx/event.h>
+#include <algorithm>
+#include <cstdlib>
+#include <cassert>
+#include "libslic3r/PrintConfig.hpp"
+#include "libslic3r/ExPolygon.hpp"
+#include <cmath>
+#include "libvgcode/include/Types.hpp"
 #if ENABLE_OPENGL_AUTO_AA_SAMPLES
 #include "GUI_Init.hpp"
 #endif // ENABLE_OPENGL_AUTO_AA_SAMPLES
@@ -280,8 +297,6 @@ bool Preview::init(wxWindow* parent, Bed3D& bed, Model* model)
     m_canvas->enable_assemble_view_toolbar(false);
 
     // sizer, m_canvas_widget
-    m_canvas_widget->Bind(wxEVT_KEY_DOWN, &Preview::update_layers_slider_from_canvas, this);
-
     wxBoxSizer *main_sizer = new wxBoxSizer(wxVERTICAL);
     main_sizer->Add(m_canvas_widget, 1, wxALL | wxEXPAND, 0);
 
@@ -516,28 +531,6 @@ void Preview::update_layers_slider_mode()
     m_layers_slider->SetModeAndOnlyExtruder(one_extruder_printed_model, only_extruder, can_change_color);
 }
 
-void Preview::update_layers_slider_from_canvas(wxKeyEvent &event)
-{
-    if (event.HasModifiers()) {
-        event.Skip();
-        return;
-    }
-
-    const auto key = event.GetKeyCode();
-
-    IMSlider *m_layers_slider = m_canvas->get_gcode_viewer().get_layers_slider();
-    IMSlider *m_moves_slider  = m_canvas->get_gcode_viewer().get_moves_slider();
-    if (key == 'L') {
-        if(!m_layers_slider->switch_one_layer_mode())
-            event.Skip();
-        m_canvas->set_as_dirty();
-    }
-    /*else if (key == WXK_SHIFT)
-        m_layers_slider->UseDefaultColors(false);*/
-    else
-        event.Skip();
-}
-
 void Preview::update_layers_slider(const std::vector<double>& layers_z, bool keep_z_range)
 {
     IMSlider *m_layers_slider = m_canvas->get_gcode_viewer().get_layers_slider();