Introduce model/ and repository/ structure under lib/

Models: Message, WikiPage, Game (typed structs instead of raw hashes)
Repositories: MessageBoard, OnlineUsers, WikiClient, CatalogClient
bbs.rb uses attribute access (page.title, game.play_path, …) throughout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/repository/message_board.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require 'csv'
+require 'time'
+require 'fileutils'
+require_relative '../model/message'
+
+class MessageBoard
+  def initialize(path)
+    @path     = path
+    @messages = []
+    @mu       = Mutex.new
+    load_csv
+  end
+
+  def append(username, text)
+    msg = Message.new(Time.now.strftime('%m-%d %H:%M'), username, text)
+    @mu.synchronize do
+      @messages << msg
+      FileUtils.mkdir_p(File.dirname(@path))
+      CSV.open(@path, 'a') { |csv| csv << [msg.timestamp, msg.username, msg.text] }
+    end
+    msg
+  end
+
+  def last(n = 30)
+    @mu.synchronize { @messages.last(n) }
+  end
+
+  def count
+    @mu.synchronize { @messages.size }
+  end
+
+  private
+
+  def load_csv
+    return unless File.exist?(@path)
+    CSV.foreach(@path) { |row| @messages << Message.new(*row) }
+  rescue => e
+    warn "MessageBoard load error: #{e}"
+  end
+end