Body rebuild step 0: Generic6DOFJoint3D on Box3D (fork patch 2) — ball w/ cone/twist + torque-capped muscle motor, weld, drive

- addons/godot-box3d/bin/libgodot-box3d.so rebuilt from fork branch generic-6dof-joint
  (weld patch + 6DOF); .vendor/box3d-generic-6dof.patch exported
- SixDofSpike: type, ball pivot/swing, cone+twist limits, muscle holds 2.94 N·m lever at 10 N·m
  cap and fails at 1.5, tracks moving target, drive follows + push-off reaction, weld rigid,
  live flag toggles — PASS x3; all existing spikes PASS x3 on the new binary
- research/godot-box3d-6dof.md (mapping, units, C# muscle recipe); HANDOFF/AGENTS pointers

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

HANDOFF.md

@@ -26,6 +26,9 @@ TERMINOLOGY (owner-corrected — use precisely):
   source + rebuild recipe + patch in `.vendor/` (`.vendor/box3d-weld.patch`,
   `.vendor/godot-box3d/`, see `research/godot-box3d-weld.md`) — **only the Linux binary is
   patched**; Windows/macOS binaries are stock (ConeTwist still errors there until rebuilt).
+  **Second patch (2026-10-02): `Generic6DOFJoint3D` → Box3D ball (spherical, cone/twist limits, torque-capped
+  motor = MUSCLE) / weld / drive (motor joint)** — fork branch `generic-6dof-joint`, `.vendor/box3d-generic-6dof.patch`,
+  details + C# muscle recipe in `research/godot-box3d-6dof.md`. Spring stiffness/damping are Box3D Hz/ratio.
   Jolt fallback = flip that one project-setting line; all gameplay code stays standard
   RigidBody3D/StaticBody3D/CharacterBody3D so the flip is lossless.
 - Runtime stack: **WiVRN + WayVR** on Linux. Headset + runtime support hand tracking (treat as available).
@@ -34,8 +37,9 @@ TERMINOLOGY (owner-corrected — use precisely):
   (`--fixed-fps 90` runs physics faster than real time at the real 90 Hz tick — the 49-scenario
   collapse spike takes seconds instead of minutes). Spikes and their pass lines:
   `physics_spike` "SPIKE: overall PASS", `weld_spike` "WELD: …", `grab_spike` "GRAB: …",
-  `body_spike` "BODY: …", `collapse_spike` "COLLAPSE: …", `arm_spike` "ARM: overall PASS".
-  All six PASS 3× as of this handoff. Headless asset import:
+  `body_spike` "BODY: …", `collapse_spike` "COLLAPSE: …", `arm_spike` "ARM: overall PASS",
+  `sixdof_spike` "6DOF: overall PASS" (run FIRST with `weld_spike` whenever the addon binary changes).
+  All seven PASS 3× as of this handoff. Headless asset import:
   `godot-mono --headless --import`.
 - Engine logs: `~/.local/share/godot/app_userdata/VR Messs/logs/godot.log` — **read after user
   playtests instead of guessing**.