Extract pages into lib/page/ modules; thin down bbs.rb

Each page is now a self-contained module with a configure(tui) class
method. Shared helpers live in TUIHelpers. bbs.rb is reduced to
constants, chrome, and wiring.

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

lib/page/online_page.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module OnlinePage
+  def self.configure(tui)
+    tui.page :online do
+      enter { @page_title = 'ONLINE USERS'; @items = ONLINE.snapshot.sort.map { |_, name| name } }
+
+      render do
+        @items.each_with_index do |uname, i|
+          you = uname == @username ? tc(:normal, ' ← you') : ''
+          text tc(:bright, uname) + you, x: CONT_X, y: CONT_Y + i
+        end
+        text "#{@items.size} user(s) online  q back",
+             x: CONT_X, y: CONT_Y + cont_h, style: THEME[:normal]
+      end
+
+      key('r')     { reload }
+      key('q')     { go :idle }
+      key(:escape) { go :idle }
+    end
+  end
+end