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

src/test/tests/test_persistence.gd

@@ -20,10 +20,13 @@ func test_save_round_trip() -> bool:
 	var last: Dictionary = results[results.size() - 1]
 	var c := TestUtils.check_eq(last.get("scenario_id", ""), "hollywood_building", "round-trips scenario id")
 	var d := TestUtils.check_eq(float(last.get("reputation", {}).get("rating", 0.0)), 82.5, "round-trips rating")
+	save.free()
 	return a and b and c and d
 
 func test_load_returns_array_when_empty_or_missing() -> bool:
 	# The tester home may already contain results; this only asserts shape safety.
 	var save := _save_instance()
 	var results: Array = save.load_shift_results()
-	return TestUtils.check(results is Array, "load_shift_results always returns Array")
+	var ok := TestUtils.check(results is Array, "load_shift_results always returns Array")
+	save.free()
+	return ok