Runtime hygiene: fix RefCounted cycles (clean suite exit), full-length shifts, wand cooldown

- FSM holds owner via WeakRef; ShiftCoordinator is RefCounted (logic-only);
  persistence tests free the Save node -> test suite exits with zero
  'resources still in use' warnings (was ~13) and 57/57 pass
- GameManager uses each scenario's shift_duration_s (900s ~ 10-15 min) for
  real shifts instead of the 300s test duration
- Wand screening gets a 0.8s recharge cooldown with a wand.recharge message
- TODO/DONE/MEMORY/README synced

content/strings.en.json

@@ -40,5 +40,6 @@
   "door.thwarted": "%s tries the locked door and fails.",
   "flashlight.on": "Flashlight on.",
   "flashlight.off": "Flashlight off.",
-  "hud.venue_switched": "Venue: %s"
+  "hud.venue_switched": "Venue: %s",
+  "wand.recharge": "Wand scanner is recharging…"
 }