Fix stale vlayer signals and index types

`LogisticFilter.signal` became `value` in 2.0, so the clear loop broke
on the first slot and outdated signals were left behind.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

exp_scenario/module/control/discord_alerts.lua

@@ -31,7 +31,7 @@ local function append_playtime(player_name)
 end
 
 --- Get the player name from an event
---- @param event { player_index: number, by_player_name: string? }
+--- @param event { player_index: uint, by_player_name: string? }
 --- @return string, string
 local function get_player_name(event)
     local player = game.players[event.player_index]