build(cloudflare): add a Cloudflare preview build target

DEPLOY_TARGET now selects the adapter; Netlify stays the default and NODE_ADAPTER
keeps working. Cloudflare compresses in transit, so the Worker build aliases
$lib/server/compression to a pass-through that leaves the streaming body alone.

CI builds and dry-run deploys this target. That is compilation and packaging
coverage only, not a production compatibility gate: native sharp still blocks the
share-preview route in the Worker runtime.

.eslintignore

@@ -11,3 +11,5 @@ node_modules
 pnpm-lock.yaml
 package-lock.json
 yarn.lock
+
+.wrangler/