Beta servers: testers can use beta features in servers whose owner opted in

- beta.Configure takes the opted-in servers; testers are looked up in the beta server
- beta commands registered per opted-in server and removed when it opts out
- beta.ServerEnabled for behaviour that no person triggers
- docs updated

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

internal/commands/betacmd/betacmd.go

@@ -6,6 +6,7 @@
 package betacmd
 
 import (
+	"fmt"
 	"sync"
 	"velox-bot/internal/beta"
 
@@ -66,12 +67,12 @@ func Handler(s *discordgo.Session, i *discordgo.InteractionCreate) {
 	switch {
 	case !isOwner(s, userID):
 		msg = "Only the bot's owner can use this command."
-	case !st.InBetaGuild:
-		msg = "Beta features aren't available here."
+	case !st.ServerEnabled:
+		msg = "Beta features are off in this server."
 	case !st.RoleConfigured:
 		msg = "No Beta Tester role is set up, so beta features are locked for everyone."
 	case st.HasRole:
-		msg = "You're a beta tester: beta features are unlocked for you in this server."
+		msg = fmt.Sprintf("You're a beta tester. Beta features are on in this server, and in %d other server(s) that opted in.", len(beta.Servers()))
 	default:
 		msg = "You don't have the Beta Tester role, so beta features are locked for you."
 	}