ludic.physics, ludic.character, ludic.vehicles: fact records reused, and phys_sink allocates nothing

The per-frame sweep over physics, character, vehicles and nav found three fact makers that made a record per fact: contacts and splashes, the character's and the vehicles'. Each keeps a pool now, as wildlife's and npc's do (q_unheld). phys_sink, asked on every removal, built two new lists each time; it filters into a kept spare pair and swaps. ludic.nav's paths and crowds already allocate nothing, and none of the four builds a string per call. What remains at load, reset or a world swap is not per frame. vehicle_feed takes its state mut. vehicles_test: 1000 fed facts, drained turn by turn, use at most 4 records. All packages 421.

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

packages/ludic.vehicles/keep.ludic

@@ -4,7 +4,7 @@
 export function vehicle_own(v: Vehicle) -> void { if v != null { v.owned = true } }
 
 # hay for a horse, up to a full belly
-export function vehicle_feed(vehicles_st: VehiclesState, v: Vehicle, amount: float) -> void {
+export function vehicle_feed(vehicles_st: mut VehiclesState, v: Vehicle, amount: float) -> void {
   if v == null { return }
   v.food = Math.min(v.food + amount, 100.0)
   ve_say(vehicles_st, VEHICLE_FED, v, amount)