init: scaffold OPENBUREAU site with shibui-derived theme

- Hugo site for openbureau.ch (Deutsch, i18n-ready for EN/IT)
- Theme themes/openbureau/ = local copy of shibui, customized via
  site-level layouts and assets to keep the theme reference clean
- Editorial typography stack: Newsreader serif body, Space Grotesk
  display, Inter for listings, IBM Plex Mono for technical meta
- Content structure: library/ (Theorie, Büroführung, Software) with
  manifest and colophon at root; software is a library category, not
  a separate top-level
- Three views over one source: Journal (chronological home),
  Library (atlas grouped by section + tag cloud), single articles

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

themes/openbureau/theme.toml

@@ -0,0 +1,21 @@
+# theme.toml template for a Hugo theme
+# See https://github.com/gohugoio/hugoThemes#themetoml for an example
+
+name = "Shibui (渋い)"
+license = "MIT"
+licenselink = "https://github.com/ntk148v/shibui/blob/main/LICENSE"
+description = "Shibui is a yet another minimalistic Hugo theme"
+homepage = "https://github.com/ntk148v/shibui"
+demosite = "https://ntk148v.github.io/shibui"
+tags = ["minimalist", "clean", "responsive", "blog", "simple"]
+features = ["responsive"]
+
+[author]
+name = "ntk148v"
+homepage = "https://github.com/ntk148v"
+
+[module]
+[module.hugoVersion]
+extended = false
+min = "0.93.0"
+