feat(engine): wire the per-filament volume-map producer pipeline

- Print::update_filament_maps_to_config takes filament/volume/nozzle
  maps, backfills an empty volume map from extruder types, rebuilds
  filament_map_2, re-expands the per-filament variant arrays, and
  recomputes retract overrides keyed by resolved slots
- grouping writes its result back in every non-sequential mode;
  manual multi-nozzle grouping validates the user mapping and raises a
  translatable error on deviation; the engine's concrete volume
  assignment is deliberately not merged yet (per-filament arrays are
  already consumed by filament id, so materializing High Flow now
  would change motion before the layer-aware resolvers land)
- Print::apply treats the three map keys as engine outputs in auto
  modes (erased from the diff and adopted), compares them against used
  filaments in manual mode, and keeps the pre-expansion snapshot in
  sync with the late normalization pass so rebuilt headers reflect the
  sliced state instead of resurrecting stale values
- volume/nozzle maps and extruder_nozzle_stats join the invalidation
  group of filament_map (wipe tower + skirt/brim)
- PresetBundle composes full configs with an optional per-filament
  volume map (plate map, else defaults derived from each extruder's
  flow type); project config keeps the map sized across filament
  count changes
- PartPlate stores per-plate volume/nozzle maps; Plater injects them
  at every slice-composition site (incl. g-code reload and wipe-tower
  estimation); BackgroundSlicingProcess reads engine results back to
  the plate in auto modes
- per-filament map trust guards relaxed to size-match everywhere now
  that every producer sizes the map; single-filament explicit flow
  assignments are honored
- tests: grouping volume maps stay concrete, merge semantics of
  update_used_filament_values, single-filament override honoring

Motion g-code is byte-identical fleet-wide including Hybrid projects
(19-fixture gate + repro determinism double-slice). Header deltas:
the map keys now dump real values, and stale pre-normalization values
(e.g. enable_prime_tower on single-used-filament prints) no longer
leak into the config block.

src/slic3r/GUI/Plater.cpp

@@ -8818,7 +8818,11 @@ unsigned int Plater::priv::update_background_process(bool force_validation, bool
     if (preset_bundle->get_printer_extruder_count() > 1) {
         PartPlate* cur_plate = background_process.get_current_plate();
         std::vector<int> f_maps = cur_plate->get_real_filament_maps(preset_bundle->project_config);
-        invalidated = background_process.apply(this->model, preset_bundle->full_config(false, f_maps));
+        std::vector<int> f_volume_maps = cur_plate->get_filament_volume_maps();
+        if (f_volume_maps.empty()) {
+            f_volume_maps = preset_bundle->get_default_nozzle_volume_types_for_filaments(f_maps);
+        }
+        invalidated = background_process.apply(this->model, preset_bundle->full_config(false, f_maps, f_volume_maps));
         background_process.fff_print()->set_extruder_filament_info(get_extruder_filament_info());
     }
     else
@@ -18326,7 +18330,11 @@ void Plater::apply_background_progress()
     Print::ApplyStatus invalidated;
     if (preset_bundle->get_printer_extruder_count() > 1) {
         std::vector<int> f_maps = part_plate->get_real_filament_maps(preset_bundle->project_config);
-        invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false, f_maps));
+        std::vector<int> f_volume_maps = part_plate->get_filament_volume_maps();
+        if (f_volume_maps.empty()) {
+            f_volume_maps = preset_bundle->get_default_nozzle_volume_types_for_filaments(f_maps);
+        }
+        invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false, f_maps, f_volume_maps));
     }
     else
         invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false));
@@ -18371,7 +18379,11 @@ int Plater::select_plate(int plate_index, bool need_slice)
         //always apply the current plate's print
         if (preset_bundle->get_printer_extruder_count() > 1) {
             std::vector<int> f_maps = part_plate->get_real_filament_maps(preset_bundle->project_config);
-            invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false, f_maps));
+            std::vector<int> f_volume_maps = part_plate->get_filament_volume_maps();
+            if (f_volume_maps.empty()) {
+                f_volume_maps = preset_bundle->get_default_nozzle_volume_types_for_filaments(f_maps);
+            }
+            invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false, f_maps, f_volume_maps));
         }
         else
             invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false));
@@ -18792,7 +18804,11 @@ int Plater::select_plate_by_hover_id(int hover_id, bool right_click, bool isModi
             //always apply the current plate's print
             if (preset_bundle->get_printer_extruder_count() > 1) {
                 std::vector<int> f_maps = part_plate->get_real_filament_maps(preset_bundle->project_config);
-                invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false, f_maps));
+                std::vector<int> f_volume_maps = part_plate->get_filament_volume_maps();
+                if (f_volume_maps.empty()) {
+                    f_volume_maps = preset_bundle->get_default_nozzle_volume_types_for_filaments(f_maps);
+                }
+                invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false, f_maps, f_volume_maps));
             }
             else
                 invalidated = p->background_process.apply(this->model(), preset_bundle->full_config(false));