fix(bots): auto-join server from channel_id so built-ins can post

Root cause: makeSender requires bot_servers membership, but create
flow never auto-added bots when users only picked a channel.

- Start() resolves config.channel_id → server and upserts bot_servers
- Confess cursor uses (created_at,id) so deletes don't stall polling

internal/bot/confess.go

@@ -21,7 +21,11 @@ func ConfessBot(ctx context.Context, db *sql.DB, raw json.RawMessage, send SendM
 		return
 	}
 
-	lastID := ""
+	// Cursor is (created_at, id) in memory so deletes don't break polling.
+	var lastAt time.Time
+	var lastID string
+	seeded := false
+
 	ticker := time.NewTicker(10 * time.Second)
 	defer ticker.Stop()
 
@@ -30,50 +34,71 @@ func ConfessBot(ctx context.Context, db *sql.DB, raw json.RawMessage, send SendM
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			confessPoll(db, cfg.ChannelID, &lastID, send)
+			confessPoll(db, cfg.ChannelID, &seeded, &lastAt, &lastID, send)
 		}
 	}
 }
 
-func confessPoll(db *sql.DB, targetChannel string, lastID *string, send SendMessageFunc) {
-	q := `SELECT id, channel_id, content FROM messages
-		WHERE content ILIKE '/confess%' AND bot_id IS NULL
-		ORDER BY created_at ASC LIMIT 10`
-	if *lastID != "" {
-		q = `SELECT id, channel_id, content FROM messages
-			WHERE content ILIKE '/confess%' AND bot_id IS NULL AND created_at::text > (SELECT created_at::text FROM messages WHERE id = $1)
-			ORDER BY created_at ASC LIMIT 10`
+func confessPoll(db *sql.DB, targetChannel string, seeded *bool, lastAt *time.Time, lastID *string, send SendMessageFunc) {
+	if !*seeded {
+		var at sql.NullTime
+		var id sql.NullString
+		_ = db.QueryRowContext(context.Background(),
+			`SELECT created_at, id::text FROM messages ORDER BY created_at DESC, id DESC LIMIT 1`,
+		).Scan(&at, &id)
+		if at.Valid {
+			*lastAt = at.Time
+		}
+		if id.Valid {
+			*lastID = id.String
+		}
+		*seeded = true
+		return
 	}
 
-	var rows *sql.Rows
-	var err error
-	if *lastID != "" {
-		rows, err = db.QueryContext(context.Background(), q, *lastID)
-	} else {
-		rows, err = db.QueryContext(context.Background(), q)
-	}
+	rows, err := db.QueryContext(context.Background(), `
+		SELECT m.id::text, m.created_at, m.content
+		FROM messages m
+		WHERE m.bot_id IS NULL
+		  AND lower(m.content) LIKE '/confess%'
+		  AND (m.created_at, m.id) > ($1::timestamptz, $2::uuid)
+		ORDER BY m.created_at ASC, m.id ASC
+		LIMIT 20
+	`, *lastAt, nullUUID(*lastID))
 	if err != nil {
 		return
 	}
 	defer rows.Close()
 
 	for rows.Next() {
-		var id, channelID, content string
-		if err := rows.Scan(&id, &channelID, &content); err != nil {
+		var id string
+		var createdAt time.Time
+		var content string
+		if err := rows.Scan(&id, &createdAt, &content); err != nil {
 			continue
 		}
+		*lastAt = createdAt
 		*lastID = id
 
-		// Strip "/confess" prefix
-		text := strings.TrimSpace(strings.TrimPrefix(content, "/confess"))
+		rest := content
+		if len(rest) >= 8 && strings.EqualFold(rest[:8], "/confess") {
+			rest = rest[8:]
+		}
+		text := strings.TrimSpace(rest)
 		if text == "" {
 			continue
 		}
 
-		// Delete the original message
-		db.ExecContext(context.Background(), `DELETE FROM messages WHERE id = $1`, id)
-
-		// Repost anonymously
+		// Delete original so author isn't exposed in chat history.
+		_, _ = db.ExecContext(context.Background(), `DELETE FROM messages WHERE id = $1::uuid`, id)
 		send(targetChannel, fmt.Sprintf("🕵️ **anonymous confession:** %s", text))
 	}
 }
+
+// nullUUID returns a zero UUID when empty so the first post-seed poll still works.
+func nullUUID(id string) string {
+	if id == "" {
+		return "00000000-0000-0000-0000-000000000000"
+	}
+	return id
+}

internal/bot/runner.go

@@ -82,6 +82,10 @@ func (r *Runner) Start(botID, botType string, config json.RawMessage) {
 	r.bots[botID] = cancel
 	r.mu.Unlock()
 
+	// Built-in bots pick a channel in config but users often skip "Add to Server".
+	// Resolve channel_id → server and ensure bot_servers so send() doesn't no-op.
+	r.ensureBotServerFromConfig(botID, config)
+
 	send := r.makeSender(botID)
 	r.logger.Info("starting built-in bot", "bot_id", botID, "type", botType)
 
@@ -96,6 +100,36 @@ func (r *Runner) Start(botID, botType string, config json.RawMessage) {
 	}()
 }
 
+// ensureBotServerFromConfig joins the bot to the server that owns config.channel_id.
+func (r *Runner) ensureBotServerFromConfig(botID string, config json.RawMessage) {
+	var cfg struct {
+		ChannelID string `json:"channel_id"`
+	}
+	if err := json.Unmarshal(config, &cfg); err != nil || cfg.ChannelID == "" {
+		return
+	}
+	serverID, err := r.hub.ServerIDForChannel(context.Background(), cfg.ChannelID)
+	if err != nil || serverID == "" {
+		r.logger.Warn("bot start: channel not found for auto-join", "bot_id", botID, "channel_id", cfg.ChannelID, "error", err)
+		return
+	}
+	var ownerID string
+	if err := r.db.QueryRowContext(context.Background(),
+		`SELECT owner_id FROM bots WHERE id = $1`, botID,
+	).Scan(&ownerID); err != nil {
+		return
+	}
+	if _, err := r.db.ExecContext(context.Background(), `
+		INSERT INTO bot_servers (bot_id, server_id, added_by)
+		VALUES ($1, $2, $3)
+		ON CONFLICT DO NOTHING
+	`, botID, serverID, ownerID); err != nil {
+		r.logger.Warn("bot start: auto-join server failed", "bot_id", botID, "server_id", serverID, "error", err)
+		return
+	}
+	r.logger.Info("bot auto-joined server", "bot_id", botID, "server_id", serverID)
+}
+
 // Stop stops a single bot by ID.
 func (r *Runner) Stop(botID string) {
 	r.mu.Lock()