fix(vagrant): substrate leg.scl cycle restored; feet inherit_scale=false

User feedback after iteration-4: legs SHOULD cycle through +1/0/-1
(substrate-style — leg renders forward, under body, then behind body).
But feet must NOT Y-flip when leg.scl_y goes negative, and must NOT
collapse when leg.scl_y=0. They should follow leg-end position only.

Three changes:
1. walk_fwd_lower keyframes restored to substrate-style (leg.scl_y
   sign-flip on both halves: leg_l +1↔-1, leg_r -1↔+1). foot.pos
   animations REMOVED — cascade through leg.world.scl now correctly
   moves foot to leg-end position automatically (foot.local.pos
   stays at rest 25 in y).
2. foot.rest.scl: [1, -1] → [1, 1] (no Y-flip in rest, natural
   sprite orientation). inherit_scale=false → foot.world.scl stays
   at foot.local.scl=[1,1] regardless of leg.scl_y. Foot sprite
   never flips, never collapses.
3. Procedural extended: writes foot.local.rot = -leg.local.rot so
   foot.world.rot = body.world.rot (feet stay body-oriented even
   when legs rotate to walk-direction).

Speed slowed further from 0.5 → 0.4 (user: still too fast at 0.5).

manifest.module

@@ -15,7 +15,7 @@
         {"id": "lib-core.camera",                 "version": "0.3.0"},
         {"id": "lib-core.render",                 "version": "0.1.0"},
         {"id": "lib-core.maps",                   "version": "0.1.2"},
-        {"id": "lib-core.puppet", "version": "0.4.2"},
+        {"id": "lib-core.puppet", "version": "0.4.3"},
         {"id": "lib-asset.prototype-subterrain",  "version": "0.1.1"}
     ]
 }