Prepare for open source: Apache-2.0 license, contributing guide, self-hosting guide, fix Close()

- LICENSE (Apache-2.0), NOTICE, CONTRIBUTING.md
- docs/self-hosting.md and README sections for hosting and contributing
- Close() no longer crashes: it only disconnects and leaves the slash commands registered, so they keep their IDs across restarts
- Tests use a neutral server ID

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

internal/bot/bot.go

@@ -21,20 +21,19 @@ import (
 )
 
 type Bot struct {
-	Session            *discordgo.Session
-	AppID              string
-	GuildID            string
-	Commands           []*discordgo.ApplicationCommand
-	registeredCommands []*discordgo.ApplicationCommand
-	Services           *services.Services
-	MusicRepo          *musicrepo.Repo
-	DBHost             string
-	LavalinkHost       string
-	LavalinkPass       string
-	betaRegistered     map[string]bool // servers where this run registered the beta commands
-	betaKnown          map[string]bool // servers where they were registered, now or in an earlier run
-	betaLoaded         bool
-	betaRoles          sync.Map // "guild:user" -> cachedRoles
+	Session        *discordgo.Session
+	AppID          string
+	GuildID        string
+	Commands       []*discordgo.ApplicationCommand
+	Services       *services.Services
+	MusicRepo      *musicrepo.Repo
+	DBHost         string
+	LavalinkHost   string
+	LavalinkPass   string
+	betaRegistered map[string]bool // servers where this run registered the beta commands
+	betaKnown      map[string]bool // servers where they were registered, now or in an earlier run
+	betaLoaded     bool
+	betaRoles      sync.Map // "guild:user" -> cachedRoles
 }
 
 func NewBot(token, appID, guildID, lavalinkHost, lavalinkPass string, cmds []*discordgo.ApplicationCommand, services *services.Services, musicRepo *musicrepo.Repo, dbHost string) (*Bot, error) {
@@ -114,14 +113,12 @@ func (b *Bot) Start() error {
 		}()
 	}
 
-	b.registeredCommands = make([]*discordgo.ApplicationCommand, len(b.Commands))
+	// Registering is an upsert by name: existing commands are updated in
+	// place and keep their IDs (links like </help:ID> keep working).
 	for _, cmd := range b.Commands {
-		created, err := b.Session.ApplicationCommandCreate(b.AppID, b.GuildID, cmd)
-		if err != nil {
+		if _, err := b.Session.ApplicationCommandCreate(b.AppID, b.GuildID, cmd); err != nil {
 			log.Printf("Cannot create '%v' command: %v", cmd.Name, err)
-			continue
 		}
-		b.registeredCommands = append(b.registeredCommands, created)
 	}
 
 	b.Session.AddHandler(commands.HandleInteraction)
@@ -428,11 +425,9 @@ func (b *Bot) removeBetaCommands(guildID string) bool {
 	return clean
 }
 
+// Close disconnects from Discord. The slash commands are left registered on
+// purpose: deleting them on every shutdown would make them disappear during a
+// restart, and registering them again would give them new IDs.
 func (b *Bot) Close() error {
-	for _, cmd := range b.registeredCommands {
-		if err := b.Session.ApplicationCommandDelete(b.AppID, b.GuildID, cmd.ID); err != nil {
-			log.Printf("cannot delete '%s' command: %v", cmd.Name, err)
-		}
-	}
 	return b.Session.Close()
 }