⚡ Bolt: Optimize historical timeseries lookup loops with O(log N) binary search

[toreleon]

💡 What: Added a findLastBarIndex binary search utility to src/data/sources/dnsePublic.ts and refactored hot loops in src/agent/backtestRunner.ts to use it instead of Array .filter().
🎯 Why: The backtest runner iterates over long historical OHLCV timeseries arrays repeatedly inside the simulation loops to find the relevant bar for the asOf time constraint. Using .filter() caused O(N) performance overhead and unnecessary memory allocations on every iteration.
📊 Impact: Reduces lookups from O(N) to O(log N) complexity, substantially accelerating backtesting times while avoiding the pressure of allocating and garbage collecting newly filtered arrays inside the inner simulation loops.
🔬 Measurement: Run pnpm test to ensure existing timing assumptions and test outputs remain entirely identical. Backtesting sessions in production will demonstrate significantly less CPU and memory overhead per turn.

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PR created automatically by Jules for task 3920530696625252141 started by @toreleon

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