feat(puppet): v0.3.0 — idle-return locomotion + version bump

- apply_locomotion idle-return: after (now - last_move_time) >
  idle_return_delay, the most-displaced planted leg steps back to its
  current hip position (over idle_step_duration). Group-stagger via
  bumping last_move_time forward by idle_return_stagger.
- M.move_to tracks p.last_move_time when position actually changes.
- README v0.3.0 changelog entry.

README.md

@@ -5,7 +5,7 @@ tracks, rest pose, keyframe animations, procedural animations
 (Lua-side), and look-at constraint. No footplant IK in v0.1
 (deferred).
 
-**Version:** 0.2.0
+**Version:** 0.3.0
 **Lib-ID:** lib-core.puppet
 **Requires:** (none — pure Lua + engine.render.*)
 **Tags:** animation, skeleton, puppet, character
@@ -125,6 +125,21 @@ ownership at write time.
 
 ## CHANGELOG
 
+### v0.3.0
+- BoneState multi-channel (rot/pos/scl) with world.scl_x/y and world.rot
+- Cascaded world-transform with scale propagation (compute_world)
+- Procedural locomotion layer via rig.locomotion block (apply_locomotion):
+  step-trigger, step-placement, step-height, leg-aim + leg-stretch
+- Idle-return logic in apply_locomotion: after (now - last_move_time) >
+  idle_return_delay, the most-displaced planted leg steps back to its hip
+  position over idle_step_duration; group-stagger via idle_return_stagger
+- M.move_to tracks p.last_move_time when position actually changes
+- Schema changes: rest.rot/scl required; legacy rest.angle rejected with
+  clear error message (Substrate-Parity v0.3.0 schema)
+- Bone-rig top-level scale field removed; per-frame world state replaces it
+- New APIs: bone_world_scale, set_foot_sprite_reach_test_only,
+  foot_state_test_only, bone_animated_test_only
+
 ### v0.2.0
 - Rig-format extension (texture, z_order, scale, anchor, asset_pack
   fields on bones; rig.bones_z_sorted for render-order)