Body step 2.3: view rides the body, mantling and climbing work

- view follows the body (deadzone, smoothed, hard 8 cm limit); no drift over
  six held poses; hanging keeps the view on the character's head
- hold-back measured at the hips, capped leg push while held, stiffer balance
- sticky legs tuck with free-space check (fixes the mantle shove loop)
- strength asymmetric by direction; structural guide strength push-only
- limb/torso friction set before AddChild (Box3D reads it only at creation)
- new phases: pose hold, hang, human-motion mantle, hand-over-hand wall climb

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

AGENTS.md

@@ -312,6 +312,11 @@ device only; the editor has an XR simulator for dev. Trackers/action map: see `x
    Rules: low-pass every feed-forward; muscles stay local to the TARGET pose (never the physical parent — rotation
    feedback); no free-path view chasing while grounded; bodies whose shapes can all be disabled need explicit
    inertia; Box3D shape queries return a null `collider` — use `collider_id`.
+   **Step 2.3:** the VIEW RIDES THE BODY (deadzone + smoothed follow + hard 8 cm `MaxViewLead`; never detach the view
+   to avoid drift — make the body able to match its pose instead); hold-back measured at the hips; sticky legs tuck
+   with a free-space check; strength asymmetric by direction (pull-down/flexion strong, raise weak; structural guide
+   strength push-only); **Box3D wrapper reads physics-material friction only at shape creation — set
+   `PhysicsMaterialOverride` before AddChild.**
    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