Fix product E2E with stale local devnet state

[FlowmemoryAI]

What changed

Fixes the second-computer product E2E failure caused by stale devnet/local/state.json files from earlier setup runs.

• Control-plane block selection now prefers a devnet source with queryable transaction IDs before falling back to empty local blocks.
• The smoke client prefetches blocks through the same JSON-RPC surface users/workbench rely on.
• Adds a regression test that writes a stale local devnet state with empty txIds and proves the smoke client still passes through committed handoff data.

Validation

Passed locally:

npm test --prefix services/control-plane
npm run flowchain:product-e2e

Why

A clean second computer is not the only install path. If a tester previously ran the older local setup, stale ignored runtime files must not break the product readiness gate.