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  HEAD's `else` block (superseded by upstream's rewritten bottom-contact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>

resources/profiles/Custom/machine/MyRepetier 0.4 nozzle.json

@@ -0,0 +1,20 @@
+{
+	"type": "machine",
+	"name": "MyRepetier 0.4 nozzle",
+	"inherits": "fdm_repetier_common",
+	"from": "system",
+	"setting_id": "GM001",
+	"instantiation": "true",
+	"printer_model": "Generic Repetier Printer",
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"printer_variant": "0.4",
+	"printable_area": [
+		"0x0",
+		"250x0",
+		"250x250",
+		"0x250"
+	],
+	"printable_height": "250"
+}

resources/profiles/Custom/machine/MyRepetier.json

@@ -0,0 +1,12 @@
+{
+	"type": "machine_model",
+	"name": "Generic Repetier Printer",
+	"model_id": "my_repetier_01",
+	"nozzle_diameter": "0.4",
+	"machine_tech": "FFF",
+	"family": "MyPrinter",
+	"bed_model": "",
+	"bed_texture": "orcaslicer_bed_texture.svg",
+	"hotend_model": "",
+	"default_materials": "Generic ABS @System;Generic PLA @System;Generic PLA-CF @System;Generic PETG @System;Generic TPU @System;Generic ASA @System;Generic PC @System;Generic PVA @System;Generic PA @System;Generic PA-CF @System"
+}

resources/profiles/Custom/machine/fdm_repetier_common.json

@@ -0,0 +1,143 @@
+{
+	"type": "machine",
+	"name": "fdm_repetier_common",
+	"inherits": "fdm_machine_common",
+	"from": "system",
+	"instantiation": "false",
+	"gcode_flavor": "repetier",
+	"disable_m73": "1",
+	"emit_machine_limits_to_gcode": "0",
+	"machine_max_acceleration_e": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_extruding": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_retracting": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_travel": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_x": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_y": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_z": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_e": [
+		"25",
+		"25"
+	],
+	"machine_max_speed_x": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_y": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_z": [
+		"12",
+		"12"
+	],
+	"machine_max_jerk_e": [
+		"2.5",
+		"2.5"
+	],
+	"machine_max_jerk_x": [
+		"9",
+		"9"
+	],
+	"machine_max_jerk_y": [
+		"9",
+		"9"
+	],
+	"machine_max_jerk_z": [
+		"0.2",
+		"0.4"
+	],
+	"machine_min_extruding_rate": [
+		"0",
+		"0"
+	],
+	"machine_min_travel_rate": [
+		"0",
+		"0"
+	],
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"printable_height": "250",
+	"extruder_clearance_radius": "65",
+	"extruder_clearance_height_to_rod": "36",
+	"extruder_clearance_height_to_lid": "140",
+	"printer_settings_id": "",
+	"printer_technology": "FFF",
+	"printer_variant": "0.4",
+	"retraction_minimum_travel": [
+		"1"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_length": [
+		"0.8"
+	],
+	"retract_length_toolchange": [
+		"2"
+	],
+	"z_hop": [
+		"0.4"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retraction_speed": [
+		"30"
+	],
+	"deretraction_speed": [
+		"30"
+	],
+	"z_hop_types": "Normal Lift",
+	"silent_mode": "0",
+	"single_extruder_multi_material": "1",
+	"change_filament_gcode": "",
+	"wipe": [
+		"1"
+	],
+	"default_filament_profile": [
+		"Generic PLA @System"
+	],
+	"default_print_profile": "0.20mm Standard @MyRepetier",
+	"bed_exclude_area": [
+		"0x0"
+	],
+	"machine_start_gcode": "M190 S[bed_temperature_initial_layer_single]\nM109 S[nozzle_temperature_initial_layer]\nG28\nG92 E0\n",
+	"machine_end_gcode": "M104 S0\nM140 S0\nG92 E0\nM84\n",
+	"layer_change_gcode": ";AFTER_LAYER_CHANGE\n;[layer_z]",
+	"before_layer_change_gcode": ";BEFORE_LAYER_CHANGE\n;[layer_z]\nG92 E0\n",
+	"machine_pause_gcode": "G91\nG1 Z10 F900\nG90\nG1 X0 Y0 F6000\n",
+	"scan_first_layer": "0",
+	"nozzle_type": "undefine",
+	"auxiliary_fan": "0"
+}