feat: Group NPC Generator — major expansion

New type:
- Street Gang: varied melee + 40% chance ranged, 7 ability pool,
  8 name parts, scavenged armour pool

Weapons & armour on all types:
- Each generated NPC now carries randomised weapons (conventional
  or integrated) and an armour description displayed on the card
- Natural weapons shown in green with paw icon
- Integrated/conventional weapons shown in blue with crosshairs

Monstaret — 6 distinct subtypes with unique profiles:
  Fang Beast, Rend Beast, Pit-Thing, Lurker, Howler, Crawler
  Each has its own stat range, natural weapons, and 4 specific abilities

Machine — 4 distinct subtypes with integrated weapon loadouts:
  Combat Unit, Scout Drone, Heavy Assault Unit, Maintenance Unit
  Each has 2-3 integrated weapons with damage/AP/range/notes

Carrion — natural weapons (Bite AP 1, Claws) + contagion/death rattle
Serial Killer — signature melee + 30% secondary ranged, body armour pool

system.json

@@ -2,7 +2,7 @@
   "id": "zero-engine",
   "title": "Zero Engine (SLA Industries)",
   "description": "A basic game system for SLA Industries using the Zero Engine rules.",
-  "version": "1.5.2",
+  "version": "1.5.3",
   "compatibility": {
     "minimum": 13,
     "verified": "14.359"