Update contract engineering post date to today

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: DexterStorey

src/lib/posts/contract-engineering.mdx

@@ -5,7 +5,7 @@ import { CopyBlock } from '~/ui/blog/copy-block'
 export const metadata = {
   title: "Contract Engineering",
   subtitle: "How we define \"done\" for AI agents using verifiable contracts",
-  date: "2026-04-07",
+  date: "2026-04-09",
   isNew: true,
   author: AUTHORS.DEXTER_STOREY,
   category: CATEGORIES.ESSAY,