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>

AGENTS.md

@@ -270,6 +270,15 @@ device only; the editor has an XR simulator for dev. Trackers/action map: see `x
    the head/neck look override exists. **HANDOFF.md at project root is the takeover document**
    (constant table verified against code — code wins on drift); keep it updated when systems
    change.
+11. **Body rebuild toward Nimso's Project TX (`research/nimso-project-tx.md`)** — step 0 DONE (fork 6-DOF joints,
+   `research/godot-box3d-6dof.md`); step 1 DONE 2026-10-02: one-time T-pose CALIBRATION persisted in a
+   gitignored `prefs.json` next to the executable (forced gate on launch, `Recalibrate()` via group
+   "calibration"), `BodyProfile` (Winter anthropometry, arm stored 1.5 cm short), shared `ArmSolver`, and the
+   TRUE BODY solver (`TrueBody.cs`: neck, chest yaw + crouch lean, lagging pelvis, moving shoulder girdle, arms)
+   with a debug skeleton. Arm-length decisions: `research/vr-avatar-arm-length.md`. Next: step 2 = the
+   muscle-driven ragdoll player (ball joints + torque-capped motors toward the True Body), replacing the
+   chase-body chest/arms/hands; ground control; then legs. Owner scope: thumbstick locomotion only, no jump,
+   avatar scaling and NPCs later.
 10. **Body physics Stage 2 — PHYSICAL ARMS, implemented 2026-10-02, awaiting owner playtest.**
    `PhysicsArms.cs`: per side an upper-arm + forearm RigidBody3D (2.0 / 1.2 kg, layer 5) that
    PD-chase their analytic 2-bone IK pose, solved each physics tick from the PHYSICAL chest