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.zones/README.md

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+# ludic.zones
+
+Where a world is simulated: a disc per player - `(x, z, r)`, `r = zones_radius(fog)`, that is the
+fog distance plus 40 m and never under 150 m, 900 m with no fog - and the discs that overlap merged
+into clusters with a bounding circle. Uses `ludic.base` and nothing else.
+
+- `zones_set(pid, x, z, r)`, `zones_clear(pid)`, `zones_reset()`; `zones_merge()` once a frame
+  after the discs are set, for the clusters.
+- `zones_contains(x, z)`: inside any disc. `zones_nearest(x, z)`: metres to the nearest disc's
+  edge, 0 inside. With no disc set, everywhere is inside (0) - a world before its first frame
+  freezes nothing.
+- `zones_clusters()`, `zones_cluster_x / _z / _r / _n(c)`, `zones_cluster_of(pid)`.
+
+The rules it keeps: fixed arrays of `ZONES_MAX` (16) slots, nothing made after the state; the
+questions allocate nothing. A world gates its ticks on `zones_contains` so what is outside every
+zone keeps its state and draws no dice.