fix(vagrant): iteration — body+head look-at, WASD-driven leg-facing, idle-collapse

- humanoid.rig.json: root removed from upper track; body look_at + slow speed
  (180 deg/s, lazy); head fast speed (480 deg/s) + +-90 deg limits; puppet
  dep bumped to 0.3.1
- animations/idle_lower.anim.json (NEW): leg+foot scl=[mirror, 0] keeps legs
  invisible at idle (locomotion skips animated bones; foot cascade zeros out)
- init.lua: set_procedural 'facing' callback writes root.rot from
  last_walk_rot_deg each frame; WASD-vector updates last_walk_rot_deg
  via atan(dx, -dy); idle_lower played parallel to idle, stopped during walk

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

animations/idle_lower.anim.json

@@ -0,0 +1,13 @@
+{
+  "id": "idle_lower",
+  "track": "lower",
+  "duration": 1.0,
+  "loop": true,
+  "keyframes": [
+    { "t": 0.0,
+      "leg_l":  {"scl": [-1, 0]},  "leg_r":  {"scl": [ 1, 0]},
+      "foot_l": {"scl": [ 1, 0], "pos": [0, 0]},
+      "foot_r": {"scl": [ 1, 0], "pos": [0, 0]}
+    }
+  ]
+}