Draft Introduction via ja-drafter/review/translate pipeline ...

Writes sections/1_introduction.tex through the documented workflow:
Japanese draft (drafts/ja/1_introduction.md), fact-check + content
review against the Notion source of truth, then English translation.
Centers the section on the proposed KSCNet architecture; open claims
without a source yet are left as inline [citation needed] markers.
Also documents the pipeline itself in CLAUDE.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>