Fix rebalance eligibility after no-order cancellation

[jackhai9]

Summary

• restart USDT rebalance qualification when a cancellation task ends with readable zero account counters
• reduce the rebalance flat-account qualification window from 3 seconds to 2 seconds
• add regression coverage for the no-orders cancellation path and update generated artifact/docs to v2.7.214

Validation

• npm test (2087 passed)
• npm run test:affected (1174 Node tests and 373 Playwright tests passed)
• npm run test:binance-orderbook-trade (855 passed)
• focused account lifecycle/rebalance/cancel Playwright coverage (58 passed)
• npm run lint:tests
• npm run build:binance-orderbook-trade
• npm run check:binance-orderbook-trade
• npm run inspect:binance-orderbook-trade
• git diff --check

Live validation

• not run; the connected Binance page and Tampermonkey installation still use the previous loaded source