fix: Godot 4.2.1 compat and map builder fixes

- Fix tab character in _build_elevated_walkways() call (line 63)
- Fix untyped 'pos' variable in grapple pillar loop (line 376)
- Remove fog_sky_affinity (Godot 4.3+ only property)
- Replace preload() with load() for runtime script loading
- Replace 'is DoubleBarrelShotgun' type check with duck-typing
- Fix 'is not OfflineMultiplayerPeer' syntax in grenade spawn
- Replace absf() with abs() in state_machine, state_air, state_ground
- Update test_level.tscn to remove stale UID reference

All fixes verified: PARSE OK and scene runs without script errors
on Godot 4.2.1 headless.

movement/player_movement_controller.gd

@@ -1112,7 +1112,7 @@ func _throw_grenade() -> void:
 	var throw_vel = camera.global_transform.basis.z * -throw_speed + Vector3.UP * throw_up_speed + velocity
 	var spawn_pos = camera.global_position + camera.global_transform.basis.z * -0.5
 	
-	if multiplayer.has_multiplayer_peer() and multiplayer.multiplayer_peer is not OfflineMultiplayerPeer:
+	if multiplayer.has_multiplayer_peer() and not (multiplayer.multiplayer_peer is OfflineMultiplayerPeer):
 		server_spawn_grenade.rpc_id(1, spawn_pos, throw_vel)
 	else:
 		_spawn_grenade_local(spawn_pos, throw_vel, 1)