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/tests/wildlife_test.ludic

@@ -10,6 +10,9 @@ program WildlifeTest {
     water: fn fk_water
     forest: fn fk_forest
     sight: fn fk_sight
+    push: fn fk_push
+    pushed_x: fn fk_pushed_x
+    pushed_z: fn fk_pushed_z
     players: fn fk_players
     player_on: fn fk_player_on
     player_x: fn fk_x
@@ -177,6 +180,25 @@ program WildlifeTest {
     expect(wildlife_seen(wildlife_st, 0))
   }
 
+  test "a walker slides round a trunk rather than through it" (wildlife_st: mut WildlifeState, wildlife_tests_fake_st: mut WildlifeTestsFakeState) {
+    fk_setup(wildlife_st, wildlife_tests_fake_st)
+    let a = deer_at(wildlife_st, 0.0, 0.0)
+    wildlife_tests_fake_st.fk_trunk = true
+    player_at(wildlife_tests_fake_st, 60.0, 0.0)
+    wildlife_tests_fake_st.fk_blocked = true
+    a.state = WILD_WANDER
+    a.tx = 0.0
+    a.tz = -100.0
+    a.timer = 100.0
+    var closest = 100.0
+    for k in 0 .. 800 {
+      wildlife_tick(wildlife_st, 0.05, 0.0)
+      closest = Math.min(closest, Math.sqrt((a.x - 0.3) * (a.x - 0.3) + (a.z + 20.0) * (a.z + 20.0)))
+    }
+    expect(closest > 1.35)
+    expect(a.z < -25.0)
+  }
+
   test "the record and the found ranges come back from the save section" (wildlife_st: mut WildlifeState, wildlife_tests_fake_st: mut WildlifeTestsFakeState) {
     fk_setup(wildlife_st, wildlife_tests_fake_st)
     wildlife_spawn(wildlife_st, 0.0, 0.0)