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/ports.ludic

@@ -63,6 +63,9 @@ export state VehiclesState {
   ve_ly: float = 0.0
   ve_lz: float = 0.0
   ve_fact_q: Queue<VehicleFact> = ve_fact_q__new()
+  ve_fpool: []VehicleFact = new []VehicleFact   # every fact record made, reused once no drain holds it
+  ve_ffree: []VehicleFact = new []VehicleFact
+  ve_fnext: int = 0
 }
 function ve__dry(x: float, z: float) -> float { return -10000.0 }
 function ve__calm(x: float, z: float, fx: float, fz: float) -> float { return 0.0 }