feat(senses): walkers slide round still things, and lines of sight are the world's to answer

- ludic.wildlife: WildlifeWorld.push / pushed_x / pushed_z (defaults change nothing); a ground
  walker's step is slid clear of a still thing with a body from its species' size and scale, and
  a step that gets nowhere turns away as the water does. Birds are not pushed; no dice added.
- ludic.npc: NpcWorld.push / pushed_x / pushed_z (a person 0.35 m round) in npc_walk, and
  NpcWorld.clear (default true), which npc_line_ok asks at 1 m so a detour does not cut a trunk.
- ludic.aim: AimView.clear replaces AimView.ground and the ground march; the pick asks the line
  a body's width short of where the ray enters the thing (aim_clear_at(t, back)), so a solid
  thing does not hide itself. probe.ludic (the ground-agreement probe) and AimView.dry are gone.
- ludic.photo: PhotoLens.clear replaces PhotoLens.ground, PhotoLens.trunk and the march.

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

packages/ludic.npc/person.ludic

@@ -19,6 +19,8 @@ export state NpcState {
   nw_ids: int = 0
   np_near_i: int = -1
   np_said: string = ""
+  np_ask_x: float = 0.0          # the point handed to NpcWorld.push, then where it came out
+  np_ask_z: float = 0.0
 }
 const NP_PI: float = 3.1415927
 const NP_TAU: float = 6.2831853