Fix keyboard input not working on Windows client

Added explicit window focus grab after connecting (lan-bootstrapper.gd)
so keyboard input is properly received by the input system.
Also added diagnostic debug prints to trace input pipeline.

examples/multiplayer-fps/scripts/weapon_manager.gd

@@ -161,6 +161,10 @@ func _rollback_tick(delta: float, tick: int, _is_fresh: bool):
 	if rollback_synchronizer.is_predicting():
 		return
 
+	# DEBUG: weapon switching
+	if input and (input.slot_1 or input.slot_2 or input.slot_3 or input.slot_4):
+		print("[WEAPON DEBUG] _rollback_tick tick=%d slots=[s1=%s s2=%s s3=%s s4=%s] active=%d inv=%s" % [tick, input.slot_1, input.slot_2, input.slot_3, input.slot_4, active_slot, inventory])
+
 	# Skip if player dead
 	if player.death_tick >= 0 and tick >= player.death_tick:
 		return
@@ -406,3 +410,8 @@ func _spawn_grenade(origin: Vector3, direction: Vector3, owner_id: int, type_idx
 	get_tree().current_scene.add_child(grenade)
 	var gtype: Grenade.GrenadeType = Grenade.GrenadeType.FLASH if type_idx == 0 else Grenade.GrenadeType.SMOKE
 	grenade.setup(origin, direction, owner_id, gtype)
+
+func _rollback_tick(delta: float, tick: int, _is_fresh: bool):
+    # DEBUG: Log when this is called with non-default input
+    if input and (input.slot_1 or input.slot_2 or input.slot_3 or input.slot_4):
+        print("[WEAPON DEBUG] _rollback_tick tick=%d slots=[%s %s %s %s]" % [tick, input.slot_1, input.slot_2, input.slot_3, input.slot_4])