fix(order-test): use live tick metadata

[SebastianBoehler]

Summary

• fetch the selected token order book, tick size, and neg_risk metadata during live market discovery
• cache that instrument metadata and pass it into CreateMarketOrderParams
• skip candidates when complete trading metadata cannot be fetched instead of falling back to fixed tick-size assumptions

Verification

• git diff --check
• cmake --build /tmp/polymarket-cpp-client-order-test-build --target order_test -j4

Live order placement was not run because --live can place a real order.