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/libslic3r/Support/TreeSupport.cpp

@@ -1,6 +1,31 @@
+#include <boost/date_time/posix_time/ptime.hpp>
+#include <boost/date_time/posix_time/posix_time_types.hpp>
+#include <cassert>
 #include <chrono>
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <map>
+#include <list>
+#include <cstdlib>
+#include <cmath>
+#include <deque>
+#include <iterator>
 #include <math.h>
 
+#include "libslic3r/Point.hpp"
+#include "libslic3r/Polygon.hpp"
+#include "libslic3r/Surface.hpp"
+#include "libslic3r/ExPolygon.hpp"
+#include "libslic3r/Line.hpp"
+#include "libslic3r/PrintConfig.hpp"
+#include "libslic3r/Geometry.hpp"
+#include "libslic3r/TriangleSelector.hpp"
+#include "libslic3r/ExtrusionEntity.hpp"
+#include "libslic3r/Flow.hpp"
+#include "libslic3r/Polyline.hpp"
+#include "libslic3r/Support/SupportParameters.hpp"
+#include "libslic3r/Utils.hpp"
 #include "format.hpp"
 #include "ClipperUtils.hpp"
 #include "Fill/FillBase.hpp"
@@ -15,10 +40,17 @@
 #include "TreeSupport.hpp"
 #include "TreeSupport3D.hpp"
 #include "BeltFloorContext.hpp"
+#include "libslic3r/libslic3r.h"
 #include <libnest2d/backends/libslic3r/geometries.hpp>
 #include <libnest2d/placers/nfpplacer.hpp>
 
 
+#include <string>
+#include <sstream>
+#include <ratio>
+#include <memory>
+#include <set>
+#include <mutex>
 #include <tbb/blocked_range.h>
 #include <tbb/concurrent_unordered_set.h>
 #include <tbb/concurrent_vector.h>
@@ -27,6 +59,11 @@
 
 #include <boost/log/trivial.hpp>
 #include <algorithm>
+#include <vector>
+#include <unordered_set>
+#include <utility>
+#include <tuple>
+#include <unordered_map>
 
 #ifndef M_PI
 #define M_PI 3.1415926535897932384626433832795
@@ -673,7 +710,7 @@ double TreeSupport::belt_floor_print_z(const Point &pos_slicing) const
     return ctx.floor_print_z(pos_slicing);
 }
 
-#define SUPPORT_SURFACES_OFFSET_PARAMETERS ClipperLib::jtSquare, 0.
+#define SUPPORT_SURFACES_OFFSET_PARAMETERS jtSquare, 0.
 void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
 {
     bool tree_support_enable = m_object_config->enable_support.value && is_tree(m_object_config->support_type.value);
@@ -2827,7 +2864,7 @@ void TreeSupport::draw_circles()
                                 Point   direction = normal(pt_on_expoly - pt_on_poly, line_width_scaled / 2);
                                 hole_lower.translate(direction);
                                 // note to expand a hole, we need to do negative offset
-                                auto hole_expanded = offset(hole_lower, -line_width_scaled / 4, ClipperLib::JoinType::jtSquare);
+                                auto hole_expanded = offset(hole_lower, -line_width_scaled / 4, jtSquare);
                                 if (!hole_expanded.empty()) {
                                     base_area_lower.holes.push_back(std::move(hole_expanded[0]));
                                     holePropagationInfos.insert({ &base_area_lower.holes.back(), {25, direction, pt_far_on_poly} });
@@ -2840,7 +2877,7 @@ void TreeSupport::draw_circles()
                                 auto&& direction = std::get<1>(holePropagationInfos[&hole]);
                                 hole_lower.translate(direction);
                                 // note to shrink a hole, we need to do positive offset
-                                auto  hole_expanded = offset(hole_lower, line_width_scaled / 2, ClipperLib::JoinType::jtSquare);
+                                auto  hole_expanded = offset(hole_lower, line_width_scaled / 2, jtSquare);
                                 Point farPoint = std::get<2>(holePropagationInfos[&hole]) + direction * 2;
                                 if (!hole_expanded.empty()) {
                                     base_area_lower.holes.push_back(std::move(hole_expanded[0]));