docs(D1-v1.0): domain pack system design — SDR template + 7 built-in packs + external pack interface

- Template approach: Semantic Document Representation (SDR)
  - Pandoc --reference-doc architecture (content/style separation)
  - Agent writes semantic Markdown, never touches format params
  - extract_style_summary() bridges reference.docx → LLM-readable style catalog
  - Jinja2 (docxtpl) preserved for fixed-structure data-fill scenarios
- Toolchain: Python stack (Pandoc + python-docx + docxtpl + openpyxl + python-pptx)
- 7 built-in packs: office.document / data.analysis / content.writing /
  research.academic / project.management / ops.devops / business.strategy
- External pack: standalone project deepagent-code-packs (not org)
- Open questions closed: template scheme / toolchain / external repo

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: lxrzlyr