ludic.npc (17.7): a person's fallback is a fact

A step round what is in the way, a target planned again after twenty seconds without progress, and a target given up are each pushed as NPC_F_STUCK (how, x, z), so the game can see where the way failed a person. The lake test expects one when a walker turns back from the water; the way test expects none when the world gives the way.

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

packages/ludic.npc/walk.ludic

@@ -46,6 +46,7 @@ export function npc_walk(npc_st: mut NpcState, p: NpcPerson, dt: float) -> void
     p.stall = p.stall + dt
     if p.stall > p.stall_max { p.stall_max = p.stall }
     if p.detours < 10 and np_detour(p, want) {
+      np_stuck_fact(npc_st, p, NPC_STUCK_DETOUR)
       p.detours += 1
       return
     }