feat(examples): add pool-code-interpreter demo

[wangdengshan]

Summary

• Add full end-to-end example showing Pool lifecycle management combined with the Code Interpreter
• Phase 1: create pool via PoolManager, list pools, wait for warm buffer, auto-scale capacity when CONCURRENCY exceeds pool_max
• Phase 2: allocate N sandboxes concurrently from the pool and run Python / TypeScript / Go snippets in parallel; report per-task and total wall-time to illustrate pool cold-start advantage
• Phase 3: kill sandboxes, delete pool (skippable via SKIP_POOL_DELETE=1)
• Configurable via env vars: SANDBOX_DOMAIN, SANDBOX_API_KEY, SANDBOX_IMAGE, POOL_NAME, CONCURRENCY, SKIP_POOL_DELETE
• Includes README with setup steps, env var table, Pool CRD YAML reference and annotated example output

Testing

• e2e / manual verification
• Verified full lifecycle: pool creation, sandbox allocation from pool, concurrent Python/TypeScript/Go execution, cleanup

Breaking Changes

• None

Checklist

• Linked Issue or clearly described motivation
• Added/updated docs (if needed)
• Added/updated tests (if needed)
• Security impact considered
• Backward compatibility considered