What changed

• Replace the homepage/docs snippet body parser with a small string scanner so Cloudflare SSR no longer imports typescript on routes that render runChain snippets.
• Add a focused regression test covering nested template expressions inside body template literals.

Why

• lab.coey.dev was returning 500 for / and /docs/patterns while /compose still worked.
• The failing routes shared src/lib/lab-chain-snippet.server.ts, which imported typescript in the server bundle. That dependency is not safe in the Cloudflare SSR runtime for these pages.
• After this change, the built server output no longer contains a typescript import for that snippet renderer, and the affected route loaders execute successfully.

Test plan

• bun test src/lib/lab-chain-snippet.server.test.ts
• bun run build
• bun run check
• Route-loader verification via direct execution of src/routes/+page.server.ts and src/routes/docs/patterns/+page.server.ts

Risk / security notes

• No capability boundary changes.
• Change is limited to server-side demo snippet parsing/highlighting for homepage and docs pages.