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.wildlife/README.md

@@ -31,6 +31,7 @@ export port WildlifeWorld {        # every member has a default: a flat dry mead
   ground, water, slope: fn(float, float) -> float     # the ground, the water's surface, the gradient
   forest: fn(float, float) -> bool
   sight: fn(ax, ay, az, bx, by, bz) -> bool           # nothing between the two points
+  push: fn(x, z, r, feet, head) -> bool, pushed_x, pushed_z   # a walker slid clear of still things
   players: fn() -> int                                # slots; player_on(p), player_x / _y / _z(p)
   hidden, noise, scent, stillness                     # per player: in a hide, 0..1, 0..1, WILD_MOVING / _STILL / _SITTING
   hour, light, winterness, wind, wind_dir: fn() -> float   # the clock, how well it sees now, the season, the weather