Add Starlight documentation site structure

- Created comprehensive Diátaxis-based documentation
- 53 pages across Tutorials, How-to, Reference, and Explanation
- Custom branding with @astrojs/discovery logo
- Pagefind search integration
- Ready for content population

docs/src/styles/custom.css

@@ -0,0 +1,68 @@
+/* Custom styles for @astrojs/discovery documentation */
+
+:root {
+	--sl-color-accent-low: #1e3a8a;
+	--sl-color-accent: #3b82f6;
+	--sl-color-accent-high: #60a5fa;
+	--sl-color-white: #ffffff;
+	--sl-color-gray-1: #f8fafc;
+	--sl-color-gray-2: #f1f5f9;
+	--sl-color-gray-3: #e2e8f0;
+	--sl-color-gray-4: #cbd5e1;
+	--sl-color-gray-5: #94a3b8;
+	--sl-color-gray-6: #64748b;
+	--sl-color-black: #0f172a;
+}
+
+/* Dark mode adjustments */
+:root[data-theme='dark'] {
+	--sl-color-accent-low: #1e3a8a;
+	--sl-color-accent: #60a5fa;
+	--sl-color-accent-high: #93c5fd;
+	--sl-color-white: #0f172a;
+	--sl-color-gray-1: #1e293b;
+	--sl-color-gray-2: #334155;
+	--sl-color-gray-3: #475569;
+	--sl-color-gray-4: #64748b;
+	--sl-color-gray-5: #94a3b8;
+	--sl-color-gray-6: #cbd5e1;
+	--sl-color-black: #f8fafc;
+}
+
+/* Code block enhancements */
+.expressive-code {
+	margin: 1.5rem 0;
+	border-radius: 0.5rem;
+	overflow: hidden;
+}
+
+/* Callout styling */
+.starlight-aside {
+	border-radius: 0.5rem;
+	padding: 1rem 1.25rem;
+}
+
+/* Enhanced card styling */
+.sl-card-grid {
+	gap: 1rem;
+}
+
+/* Table of contents styling */
+.right-sidebar {
+	border-left: 1px solid var(--sl-color-gray-3);
+}
+
+/* Better link hover states */
+a:hover {
+	text-decoration: underline;
+	text-decoration-thickness: 2px;
+	text-decoration-color: var(--sl-color-accent);
+}
+
+/* Page header styling */
+.content-panel h1 {
+	background: linear-gradient(135deg, var(--sl-color-accent) 0%, var(--sl-color-accent-high) 100%);
+	-webkit-background-clip: text;
+	-webkit-text-fill-color: transparent;
+	background-clip: text;
+}