Body step 1: one-time T-pose calibration (prefs.json, forced gate) + True Body solver + shared ArmSolver

- BodyProfile (Winter anthropometry, T-pose: arm = (span - shoulder width)/2 - 1.5 cm) and
  Prefs (gitignored prefs.json next to the executable / project folder in editor builds)
- Calibration node: loads prefs, else head-locked prompt + jitter-proof TPoseDetector; body
  systems wait for BodyProfile.Current; Recalibrate() in group "calibration"; recal rebuilds arms
- ArmSolver: PhysicsArms' elbow solve extracted (behaviour-identical) + min reach |U-F| fix
- TrueBody: derived real-body pose (neck, chest yaw + crouch lean at neck pivot, lagging pelvis,
  moving shoulder girdle with scapulohumeral shrug, arms) + debug skeleton
- PhysicsArms/PhysicsTorso/BodyRig now profile-driven (arm length no longer from head height)
- TrueBodySpike PASS x3; all spikes PASS x3 (arm spike thresholds re-based for correct 0.57 m arms;
  CollapseSpike uses a fixed standing profile)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scenes/main.tscn

@@ -1,4 +1,4 @@
-[gd_scene load_steps=21 format=3]
+[gd_scene load_steps=23 format=3]
 
 [ext_resource type="Script" path="res://scripts/Main.cs" id="1_main"]
 [ext_resource type="PackedScene" path="res://scenes/teleport_marker.tscn" id="2_marker"]
@@ -11,6 +11,8 @@
 [ext_resource type="Script" path="res://scripts/BodyRig.cs" id="9_bodyrig"]
 [ext_resource type="Script" path="res://scripts/PhysicsTorso.cs" id="10_physicsTorso"]
 [ext_resource type="Script" path="res://scripts/PhysicsArms.cs" id="11_physicsArms"]
+[ext_resource type="Script" path="res://scripts/Calibration.cs" id="12_calibration"]
+[ext_resource type="Script" path="res://scripts/TrueBody.cs" id="13_truebody"]
 
 [sub_resource type="ProceduralSkyMaterial" id="ProceduralSkyMaterial_sky"]
 sky_horizon_color = Color(0.66, 0.72, 0.81, 1)
@@ -122,6 +124,12 @@ script = ExtResource("10_physicsTorso")
 [node name="PhysicsArms" type="Node" parent="."]
 script = ExtResource("11_physicsArms")
 
+[node name="Calibration" type="Node" parent="."]
+script = ExtResource("12_calibration")
+
+[node name="TrueBody" type="Node3D" parent="."]
+script = ExtResource("13_truebody")
+
 [node name="BodyRig" type="Node3D" parent="."]
 script = ExtResource("9_bodyrig")
 

scenes/truebody_spike.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://scripts/TrueBodySpike.cs" id="1_spike"]
+
+[node name="TrueBodySpike" type="Node"]
+script = ExtResource("1_spike")