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>

site/content/_index.md

@@ -0,0 +1,42 @@
+---
+title: "Agentic Semantic Web"
+description: "Semantic HTML, data-* attributes, and CSS-only styling for the agentic era."
+date: 2026-04-10
+tags: ["asw", "semantic-web", "html"]
+
+---
+
+# Agentic Semantic Web
+
+**ASW** is a vocabulary and design system for the agentic era — semantic HTML with `data-*` attributes, CSS-only styling, no JavaScript required where a browser element already does the job.
+
+Built for sites generated by agents and read by agents. Navigable by humans.
+
+## What this is
+
+- [Docs](/docs/) — the ASW HTML vocabulary, layout system, and components
+- [Vault](/notes/) — live ASW notation: task lists, sessions, diffs, wikilinks
+- [Posts](/articles/) — writing and vocabulary reference
+- [Papers](/essays/) — longer-form thinking on the semantic web
+
+## The design principle
+
+No invented CSS classes. Every style target is either a semantic HTML element or a `data-*` attribute:
+
+```html
+<aside data-callout="note">This is a note.</aside>
+<section data-layout="grid">...</section>
+<a data-wikilink href="/notes/session/">session log</a>
+```
+
+Agents read the attributes. Humans read the content. The CSS connects them.
+
+## Try the shortcodes
+
+{{< callout note >}}
+This is a **note callout** rendered via the `callout` shortcode. Output: `<aside data-callout="note">`.
+{{< /callout >}}
+
+{{< callout tip >}}
+See the [Getting Started](/articles/getting-started/) post to wire ASW into your Hugo project.
+{{< /callout >}}