ludic.base, ludic.wildlife, ludic.npc: fact records reused, not made per fact

wl_fact made a new WildFact per fact, about one a frame, and Ludic never gives one back. ludic.base's q_unheld(q, pool, out) lists the records a queue no longer holds: neither waiting nor handed out by its last drain, which is good until the next drain. ludic.wildlife and ludic.npc now keep a pool, hand out a free record, and make a new one only when every record is held. Taking a record writes the state, so wl_fact / np_fact and the few callers holding their state read-only take it mut. Tests: q_unheld's rules (an empty drain holds on, the safe side); 3000 prints drained frame by frame use at most 4 records; 500 arrivals drained turn by turn use at most 4. base 37, wildlife 27, npc 17; all packages 420.

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

packages/ludic.npc/act.ludic

@@ -30,7 +30,7 @@ function np_turns(act: int) -> bool {
 }
 
 # a player who came within notice since the last look is greeted - once, until they walk off
-export function npc_notice(npc_st: NpcState, p: NpcPerson) -> void {
+export function npc_notice(npc_st: mut NpcState, p: NpcPerson) -> void {
   let reach = NpcKinds[p.kind].notice
   for i in 0 .. NpcWorld.players() {
     if i >= 30 { break }