Migrate docs site to Hugo Hinode

[adonm]

Summary

• migrate the documentation site from mdBook to Hugo using Hinode as a Hugo module
• move Markdown into the standard content/docs/ Hugo structure with front matter and section indexes
• preserve the old mdBook/SUMMARY navigation order with Hugo weights and printable ordering
• preserve mdBook-style public URLs such as /security/001-isolation.html, /operations/010-configmgmt.html, /CONTRIBUTING.html, /compliance-mapping.html, and /glossary.html
• keep /docs/.../ aliases for backwards compatibility while generated navigation and sampled page links avoid /docs/ URLs
• convert D2 diagrams to Mermaid code fences and enable Hinode Mermaid rendering
• replace the generated release PDF with a /printable/ long-page print/save-as-PDF view
• simplify site chrome: text title instead of Hinode logo, no copyright footer, no GitHub/social footer, and hidden navbar/footer chrome in print output
• manage Hugo Extended, Sass, and Cargo-installed tooling through mise (hugo-extended, npm:sass-embedded, cargo-binstall, cargo:rumdl)
• update CI, build tooling, ignores, README, and content checks for Hugo

Reviewer notes

• The large diff is mostly the expected mdBook-to-Hugo content move plus front matter and URL/link updates.
• Generated output is intentionally not committed; public/, resources/, hugo_stats.json, and .hugo_build.lock are clean.
• Custom layout overrides are intentionally small and localised:
  • layouts/_default/printable.html
  • layouts/index.html
  • layouts/_partials/assets/breadcrumb.html
  • layouts/_partials/footer/footer.html
  • layouts/_partials/footer/social.html
  • layouts/_partials/utilities/GetPage.html

Validation

• python3 scripts/check-content.py
• mise exec -- hugo --minify
• git diff --cached --check
• verified docs and printable page order: intro, architecture principles, security, operations, development, reference architectures, templates, contributing, compliance, glossary
• verified mdBook-compatible generated output paths exist, including representative ADRs and top-level pages
• verified generated page links sampled from home and ADR pages do not point at /docs/
• verified printable output has no footer/social chrome and no copyright footer text
• verified Mermaid markup and runtime assets are present in generated ADR and printable pages

Notes

• Supersedes Migrate docs site to Hugo Hinode #20, whose old source branch was removed during the requested branch rename/history cleanup.
• Hugo emits upstream Hinode/module deprecation warnings for module.mounts.includeFiles, .Site.Data, and .Site.Languages; the build completes successfully.
• lychee reports redirects only; no link errors.