test: build live captures from probe events

[jackhai9]

Summary

• derive strict Stage 4 live-performance captures directly from semantic probe events
• bind each scenario kind to an exact wall-clock segment contract
• read live feedback from the dedicated userscript status node
• document the capture-builder workflow and remove an obsolete empty-ledger claim

Validation

• npm test (343/343)
• npm run test:ui (51/51)
• npm run check:binance-orderbook-trade
• targeted capture-builder tests (18/18)
• targeted live probe UI tests (5/5)
• git diff --check