refactor: restructure repo into src/ site/ dist/ vendor/ packs/

Separate framework source from website:
- src/layers/ + src/main.css: CSS framework source (was assets/css/)
- site/: Hugo website (content/, layouts/, hugo.toml)
- dist/: built output (asw.css, asw.min.css)
- vendor/open-props/: vendored dependency with version tracking
- Hugo module mounts: dist/ → static, site runs from site/

Build: hugo --source site/ passes (105 pages).
npm run build produces dist/asw.css.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

layouts/partials/meta/ai-disclosure.html

@@ -1,25 +0,0 @@
-{{- /*
-  partials/meta/ai-disclosure.html — AI-generated content disclosure
-
-  Emits the proposed W3C/WHATWG AI content disclosure meta tag and the
-  corresponding HTTP-equiv header that satisfies EU AI Act Article 50
-  obligations for AI-generated/AI-assisted web content.
-
-  The disclosure level is controlled per-page via front matter:
-    ai_content: "generated"   — fully AI-generated content
-    ai_content: "assisted"    — human-written with AI assistance (default)
-    ai_content: "reviewed"    — AI-generated, human-reviewed and edited
-    ai_content: "none"        — no AI involvement (suppresses the tag)
-
-  Site-wide default in hugo.toml:
-    [params]
-      ai_content = "assisted"   # default for all pages
-
-  Reference:
-    https://github.com/nickvdyck/ai-content-disclosure
-    EU AI Act Article 50 (transparency obligations, Chapter IV)
-*/ -}}
-{{- $level := or .Params.ai_content .Site.Params.ai_content "assisted" -}}
-{{- if ne $level "none" -}}
-<meta name="ai-content-disclosure" content="{{ $level }}">
-{{- end }}