Add landing page + Starlight docs site (#375)

* udpated matrix

* feat(site): add landing page + Starlight docs site

Astro + Starlight site in site/ — a flat/paper editorial landing page
plus 18 docs pages seeded from the README. Monochrome theme, hairline
rules, square corners, live GitHub star count, light default + dark
toggle. Deploys to GitHub Pages via .github/workflows/deploy-site.yml.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

site/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "site",
+  "type": "module",
+  "version": "0.0.1",
+  "scripts": {
+    "dev": "astro dev",
+    "start": "astro dev",
+    "build": "astro build",
+    "preview": "astro preview",
+    "astro": "astro"
+  },
+  "dependencies": {
+    "@astrojs/starlight": "^0.39.2",
+    "@fontsource-variable/archivo": "^5.2.8",
+    "@fontsource/ibm-plex-mono": "^5.2.7",
+    "astro": "^6.3.1",
+    "sharp": "^0.34.5"
+  }
+}