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.aim/pick.ludic

@@ -1,5 +1,5 @@
 # pick.ludic - one target a frame: the game offers every candidate, and the nearest one the ray enters
-# that the ground does not hide is the pick. Near things occlude far ones for free, which is what a
+# that nothing hides is the pick. Near things occlude far ones for free, which is what a
 # player means by "I am looking at that one".
 export const AIM_NONE: int = 0
 export const AIM_REACH_MIN: float = 3.0     # about as far as a hand goes with a step into it
@@ -13,9 +13,6 @@ export state AimState {
   am_dist: float = 0.0
   am_reach: bool = false
   am_off: float = 1.0
-  am_seen: int = 0
-  am_blocked: int = 0
-  am_disagree: int = 0
 }
 
 # The crosshair decides WHICH; the distance decides only WHETHER. Every reach is lifted to a floor of
@@ -41,7 +38,7 @@ export function aim_offer(aim_st: mut AimState, kind: int, id: int, x: float, y0
   let rr = r + aim_slack_m(d)
   let hit = aim_ray_cyl(x, y0, y1, z, rr)
   if hit < 0.0 or not (hit < aim_st.am_t) { return false }
-  if not aim_clear_to(x, (y0 + y1) * 0.5, z) { return false }
+  if not aim_clear_at(hit, rr) { return false }
   aim_st.am_t = hit
   aim_st.am_off = aim_miss(x, z, rr)
   aim_st.am_kind = kind