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>

AGENTS.md

@@ -25,6 +25,9 @@ embodiment/view system in particular is theory until proven.
   `https://github.com/Foxyz1302/godot-box3d` (branch `rigid-weld-joint`, carries the weld
   patch; PR to upstream pending, owner-side) — and it may gain more additions in the future
   (rebuild recipe + source in `.vendor/`, only the Linux binary is patched locally).
+  Patches so far: ConeTwistJoint3D → rigid weld (`research/godot-box3d-weld.md`), Generic6DOFJoint3D →
+  ball/weld/drive with torque-capped muscle motors (`research/godot-box3d-6dof.md`, regression
+  `scenes/sixdof_spike.tscn`).
   Jolt (built-in) is the fallback: reverting is
   the one project-setting line, and all gameplay code must stay standard-Godot-physics-node
   based so that flip is lossless.