ludic.wildlife (18.2): a walker a crowd moves

wildlife_set_crowd(a, true) hands a walker to a crowd. Its step no longer moves it, and its want is two fields on it: goal_x / goal_z (the point it heads for or faces) and goal_speed (0 when it stands). A route reads those and hands back where the crowd put it through wildlife_moved(a, x, z, vx, vz). That sets its place, its ground, its heading from its velocity and its prints, and updates its row's columns so the spatial index finds it there. Nothing allocates per animal per frame: the want is the animal's own fields, and moved writes in place. The prints and the turn counters moved to walked.ludic (steer.ludic was at the 100-line limit). crowd_test holds it; with crowd off every old test is unchanged. wildlife 26/26.

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

packages/ludic.wildlife/walked.ludic

@@ -0,0 +1,42 @@
+# walked.ludic - what a step leaves behind (a print every 2.8 m), how often a step was refused, and
+# the crowd's side (phase 18): a crowd walker only says where and how fast, and is handed back where
+# the crowd put it. Nothing here allocates: it runs for every walker every frame.
+
+# how many steps were refused and turned from since the start: how often the way was not enough
+export function wildlife_turned(wildlife_st: WildlifeState) -> int { return wildlife_st.wl_turned }
+# of those, how many for water ahead and how many for a climb (the rest: pushed back by a still thing)
+export function wildlife_turned_wet(wildlife_st: WildlifeState) -> int { return wildlife_st.wl_turned_wet }
+export function wildlife_turned_steep(wildlife_st: WildlifeState) -> int { return wildlife_st.wl_turned_steep }
+
+# d metres covered: a print when it has gone far enough since the last
+function wl_walked(wildlife_st: mut WildlifeState, a: WildAnimal, s: WildSpecies, d: float) -> void {
+  a.track_d = a.track_d + d
+  if s.tracks and a.track_d > 2.8 {
+    a.track_d = 0.0
+    wl_fact(wildlife_st, WILD_PRINT, a)
+  }
+}
+
+# a crowd walker's step: its want is where it faces or heads (goal_x / _z) at this tick's speed
+function wl_crowd_step(a: WildAnimal) -> bool {
+  a.goal_speed = a.speed
+  return true
+}
+
+# walked by a crowd, or by its own step again (off, it keeps where the crowd left it)
+export function wildlife_set_crowd(a: WildAnimal, on: bool) -> void { a.crowd = on }
+
+# where the crowd put a walker, and how fast it went: its place, its heading from its velocity, its
+# ground from the world's, and its prints as it goes
+export function wildlife_moved(wildlife_st: mut WildlifeState, a: WildAnimal, x: float, z: float, vx: float, vz: float) -> void {
+  let dx = x - a.x
+  let dz = z - a.z
+  let d = Math.sqrt(dx * dx + dz * dz)
+  a.x = x
+  a.z = z
+  a.y = WildlifeWorld.ground(x, z)
+  if vx * vx + vz * vz > 0.01 { a.yaw = Math.atan2(-vx, -vz) }
+  let r = wl_row(a)
+  if r >= 0 { tb_set_xz(a.tab, WA_X, WA_Z, r, x, z) }
+  wl_walked(wildlife_st, a, wl_sp(wildlife_st, a.sp), d)
+}