wip: course website (incomplete — Task 15 in progress)

Partial: Astro Starlight config, sync-content.mjs + 6 passing tests.
Missing: pages (index, disclaimer, about), harness page, lockfile,
verified build. See SDD ledger.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

site/src/content.config.ts

@@ -0,0 +1,7 @@
+import { defineCollection } from "astro:content";
+import { docsLoader } from "@astrojs/starlight/loaders";
+import { docsSchema } from "@astrojs/starlight/schema";
+
+export const collections = {
+  docs: defineCollection({ loader: docsLoader(), schema: docsSchema() }),
+};