Body step 2: the player is a muscle-driven ragdoll (Project TX)

PlayerRagdoll: 9 bodies, spine/neck ball joints, shoulder drives (girdle + muscle),
elbow hinges, torque-capped motor PDs toward the True Body, chest->hand guides,
implicit balance motor, mass-scaled ground control. PlayerRig: XR driver with
stick move / snap turn and Bonelab-style push-back (eye->camera sphere sweep).
Replaces the chase bodies in main.tscn; RagdollSpike regression (14 phases).

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

AGENTS.md

@@ -103,8 +103,9 @@ Four layers, bottom-up, applied per frame in this order:
    project: chain budgets, screen-size/distance LOD, simplified colliders. If the per-bone C#
    loop profiles hot, the hot loop moves to a GDExtension — profile first, don't pre-optimize.
 
-Do NOT build anything that needs 6DOF/cone-twist joints between tracked bodies (the wrapper lacks
-them; velocity steering replaces them). Scene objects stay standard nodes (`RigidBody3D`,
+SUPERSEDED for the player (2026-10-02): the fork now maps Generic6DOFJoint3D (ball/drive/weld), and the
+player body is a jointed muscle ragdoll (item 11). Layer 3 above describes the legacy chase bodies, which
+remain valid for non-player things (and their spikes). Scene objects stay standard nodes (`RigidBody3D`,
 `StaticBody3D`, `CharacterBody3D`) so arbitrary imported scene content works and the Jolt fallback
 stays real.
 
@@ -289,10 +290,15 @@ device only; the editor has an XR simulator for dev. Trackers/action map: see `x
    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.
+   with a debug skeleton. Arm-length decisions: `research/vr-avatar-arm-length.md`. **Step 2 DONE 2026-10-02
+   (awaiting owner playtest): the player IS a muscle-driven ragdoll** — `PlayerRagdoll.cs` (9 bodies, BALL/hinge/
+   DRIVE joints with torque-capped motor PDs toward the True Body, chest→hand guides, implicit balance, ground
+   control) + `PlayerRig.cs` (XR driver: stick move/snap turn, Bonelab push-back via an eye→camera sphere sweep,
+   discrete origin jumps carry the body). It REPLACED PhysicsHands/PhysicsTorso/PhysicsArms/BodyRig in
+   `main.tscn` (legacy files kept for their spikes). Record + measured rules:
+   `research/ragdoll-player-step2.md` — **never put a light (< ~1 kg) body between two strong motors** (Box3D
+   one-iteration substeps oscillate). Regression `scenes/ragdoll_spike.tscn`. Next: procedural legs, 144 Hz,
+   climbing. 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