Replace display.rb with DSL primitives in bbs.rb

All content rendering now lives in bbs.rb via the rubbs DSL.
fetch/pick handle wiki list + article drill-down; output handles
the multi-line game catalog. display.rb is gone.

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

Gemfile.lock

@@ -1,6 +1,6 @@
 GIT
   remote: https://git.teletype.hu/tools/rubbs.git
-  revision: d9232eabb4ddba2b860921657cf20fe7f3cbd830
+  revision: 272e75bd6f90a235eeac684d412ceb04c146c926
   specs:
     bbs (0.1.0)
       artii (~> 2.1)