chore(prompts-core): wire markdown prompt packaging

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/markdown.d.ts

@@ -0,0 +1,4 @@
+declare module "*.md" {
+  const markdown: string
+  export default markdown
+}