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/src/lib/github.ts

@@ -0,0 +1,42 @@
+/**
+ * Build-time GitHub star count. Fetched once when the site is built (the GitHub
+ * Actions runner has network); falls back to a constant locally / offline so a
+ * build never hangs or fails on the network. The result is memoized for the
+ * lifetime of the build process, so rendering it on every page is a single API
+ * call, not one per page.
+ */
+function format(n: number): string {
+	if (n >= 1000) {
+		const k = n / 1000;
+		const rounded = k >= 10 ? Math.round(k) : Math.round(k * 10) / 10;
+		return `${String(rounded).replace(/\.0$/, '')}k`;
+	}
+	return String(n);
+}
+
+async function fetchStars(fallback: string): Promise<string> {
+	try {
+		const controller = new AbortController();
+		const timeout = setTimeout(() => controller.abort(), 3000);
+		const res = await fetch('https://api.github.com/repos/colbymchenry/codegraph', {
+			headers: {
+				Accept: 'application/vnd.github+json',
+				'User-Agent': 'codegraph-site',
+			},
+			signal: controller.signal,
+		});
+		clearTimeout(timeout);
+		if (!res.ok) return fallback;
+		const data = (await res.json()) as { stargazers_count?: number };
+		return typeof data.stargazers_count === 'number' ? format(data.stargazers_count) : fallback;
+	} catch {
+		return fallback;
+	}
+}
+
+let cached: Promise<string> | null = null;
+
+export function getStarsLabel(fallback = '22k'): Promise<string> {
+	cached ??= fetchStars(fallback);
+	return cached;
+}