ludic.zones: a disc per player from their fog, merged into clusters; the simulating packages ask whether a place is simulated

zones_set / zones_clear / zones_merge, zones_contains / zones_nearest and the clusters' bounding circles,
over fixed arrays of ZONES_MAX (16). WildlifeWorld.active freezes an animal outside (no state change, no
dice), NpcWorld.active a walker (and no birth outside), VehicleWorld.active a moored boat, and
ThingsWorld.restocks keeps a morning's restock inside; every default is "everywhere", so an unbound game
is unchanged. Tests: the merge (near players one cluster, far two, a player leaving splits a chain),
contains, nearest, the radius; wildlife, npc, vehicles and things pass as before.

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

packages/ludic.things/port.ludic

@@ -5,6 +5,7 @@ export port ThingsWorld {
   placed: fn(Thing) -> void = fn th_nothing           # a Thing exists now: draw it
   removed: fn(Thing) -> void = fn th_nothing          # it is gone for good: stop drawing it
   shown: fn(Thing) -> void = fn th_nothing            # its `active` changed: show or hide it
+  restocks: fn(float, float) -> bool = fn th_yes2      # a morning restocks here (inside a zone)
   moved: fn(Thing) -> void = fn th_nothing            # it stands somewhere else now
   keeps: fn(Thing) -> bool = fn th_kind_saves         # the save's section carries it
   put_down: fn(Thing) -> bool = fn th_kind_put_down   # set down by someone: a restock leaves it be
@@ -12,5 +13,6 @@ export port ThingsWorld {
 }
 function th_flat(x: float, z: float) -> float { return 0.0 }
 function th_nothing(t: Thing) -> void { }
+function th_yes2(x: float, z: float) -> bool { return true }
 function th_kind_saves(t: Thing) -> bool { return thing_kind_ok(t.kind) and ThingKinds[t.kind].saved }
 function th_kind_put_down(t: Thing) -> bool { return thing_kind_ok(t.kind) and ThingKinds[t.kind].put_down }