feat(cloudflare): add React frontend and improve deployment docs

- Add React + Vite frontend for Cloudflare example with sandbox-agent SDK
- Update ensureRunning to poll health endpoint instead of fixed wait
- Fix SDK fetch binding issue (globalThis.fetch.bind)
- Update docs with .dev.vars format warning and container caching tip
- Use containerFetch proxy pattern for reliable local dev

docs/docs.json

@@ -49,9 +49,9 @@
 					"deploy/index",
 					"deploy/local",
 					"deploy/e2b",
+					"deploy/daytona",
 					"deploy/vercel",
 					"deploy/cloudflare",
-					"deploy/daytona",
 					"deploy/docker"
 				]
 			},