Add an "Alternatives considered" section enumerating the design
options from issue #88 (duplicate bottles / agent-side bottle_config
/ bottle-side extends) and why extends won, so the PRD stands without
the forge thread. Repoint the two phrases that depended on the #88
comment thread at the new section.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>